President Bashar al-Assad has announced his candidacy for presidential elections in June, confirming his intention to stay in office despite years of civil war.
With President Assad determined to remain in power, will the regime or the rebels ever be capable of gaining the upper hand?
BBC Diplomatic correspondent James Robbins explains.
Social media networks have been embraced enthusiastically by foreign fighters in Syria's conflict A report has cast unprecedented light on how foreign fighters engaged in the Syria conflict are using social media. The International Centre for the Study of Radicalism report says they are using social media to document their role in the conflict in real time.
The report reveals high numbers are getting information from unofficial "disseminators", individuals not affiliated to any militant group.
It identifies spiritual authorities who fighters look to for guidance.
"This is the most socially mediated conflict in history," Shiraz Maher, one of the report's authors, told BBC Newsnight, "they want to use it in order to inspire people to come out and join their cause."
Data from 114 individuals was analysed by the ICSR, comprising 121 unique accounts - 86 from Facebook and 35 from Twitter. The researchers mapped foreign fighters' social media connections, who they follow and who follow them.
Country of originTheir analysis reveals the majority of the individuals come from the UK (25.4%), followed by France (14%), Germany (12.3%), Sweden (8.8%), Netherlands (7%), and Belgium (5.3%).
Continue reading the main story Jihadist group active in Iraq and SyriaFormed in April 2013 and grew out of al-Qaeda's affiliate organisation in IraqLeader is Abu Bakr al-BaghdadiEstimated number of fighters is 3,000 to 5,000Mostly active in northern and eastern provinces of SyriaEastern European countries (Albania, Bosnia, Bulgaria, Kosovo, Macedonia, Serbia) collectively comprised 6.1%, while non-European Westerners (Australians, Canadians, and US Americans) accounted for 7%.It was not possible to determine the country of origin of 13.2 %.
Security chiefs in Whitehall believe the number of British men thought to have fought in Syria has now reached the upper end of the low hundreds.
So far this year, more than 30 people have been arrested in Britain on suspicion of terror offences, compared with 24 in the whole of 2013.
In terms of group affiliation, the ICSR analysis shows that 61.4% of foreign fighters in the sample were identified as members of rebel jihadist group the Islamic State in Iraq and the Levant (Isis), while 17.5% were thought to belong to the Al-Nusra Front, a rival group, linked to al-Qaeda that has become a key player in the conflict.
"The overwhelming majority within our database belong to Isis... they are very willing to take foreign fighters," Shiraz Maher says.
Some 29% of the fighters analysed could not be coded as belonging to any group, while the Free Syrian Army, Liwa al-Tawheed and Ahrar al Shamm comprised 2% of the total sample combined.
'New disseminators'The academic analysis also reveals the official Twitter accounts of jihadist groups are less important as sources of information for foreign fighters in Syria, than so-called "disseminator accounts" run by sympathetic individuals who lend moral and political support to those involved in the conflict.
Continue reading the main story Aims to establish Islamist state in SyriaLeader: Abu Mohammad al-Julani5,000 official members (approx.), supported by thousands of othersApparently has members inside government and militaryBig guerrilla attacks on rural government targets; lower level urban attacksUses car bombings, suicide attacks, targets media facilities and personalitiesPolicy of silenceThese accounts spread real-time information from the battlefield, publish links to new videos and official statements, and share photographs of battles, equipment and meetings.Examining the 32 most popular accounts followed on Twitter by foreign fighters in the dataset, 11 of those are "disseminator" accounts, with only one being the official account of a fighting group.
Of the 12 most popular disseminators, six are among the most mentioned and re-tweeted accounts by foreign fighters.
New spiritual authoritiesThe ICSR discovered three of the top 10 most liked Facebook pages by foreign fighters in their sample belong to religious figures, suggesting there is an emerging set of new clerical authorities who foreign fighters in Syria consider important and influential sources of religious and political motivation and support.
These include two preachers who both speak English and regularly communicate with Western Muslim audiences through social media platforms.
Ahmad Musa Jibril, a Palestinian-American cleric who is in his early 40s, is followed on Twitter by 60% of foreign fighters, the academics say.
The ICSR report says he does not openly incite his followers to violence nor does he explicitly encourage them to join the Syrian jihad. Instead, he adopts the role of a cheerleader, supporting the principles of armed opposition to Assad.
Ifthekar Jaman was killed fighting in Syria shortly after speaking to BBC NewsnightMusa Cerantonio, a 29-year-old Australian convert to Islam who frequently appears on satellite television has become an outspoken supporter of Isis, because he says it aims to create a regional Islamic state or caliphate. He is followed on Twitter by 23% of foreign fighters in the sample.
The report authors stress that these findings should not suggest that either individual is a member of Isis or the al-Nusrah Front, nor that it should be taken as indicating that they are involved in facilitating the recruitment of foreign fighters.
A pointed example of Mr Jibril's interaction with a foreign fighter came after the death in December last year of Ifthekar Jaman, a British man who told BBC Newsnight he was "doing his duty" by fighting for a group linked to al-Qaeda in Syria.
Within hours of Ifthekar's death Ahmad Musa Jibril sent a message of condolence via direct message on Twitter to Ifthekar's brother, which was then published publically on Ifthekar's brother's timeline.
Mr Jibril did not respond to BBC Newsnight's invitation for an interview. Mr Cerantonio declined to give an interview. He said although he supports Isis he has also been critical of the group.
The Newsnight report from Tuesday 15 April 2014 is available to watch on BBC iPlayer and Newsnight website.
The photos are among 55,000 digital images apparently provided by a former Syrian police photographer Graphic photographs of prisoners allegedly tortured by Syrian government forces have been shown to members of the UN Security Council.The images, reportedly smuggled out by a defector, appear to show evidence of abuse, including beatings, strangulation and long-term starvation.
The photos were first released in January in a report commissioned by Qatar, which backs Syria's opposition.
The Syrian government has dismissed the report, saying it has no credibility.
The meeting was called by France, which wants the International Criminal Court (ICC) to investigate crimes against humanity.
President Bashar al-Assad's main ally, Russia, has the power to veto that.
'Gruesome'Security Council members fell silent as the images were shown on Tuesday, said France's UN ambassador, Gerard Araud.
Investigators have examined thousands of images of dead prisoners "The gruesome images of corpses bearing marks of starvation, strangulation and beatings... indicate that the Assad regime has carried out systematic, widespread and industrial killing," said Samantha Power, US ambassador to the UN.
"Nobody who sees these images will ever be the same."
'Credible'The report, by three former war crimes prosecutors, is based on the evidence of a defected military police photographer, referred to only as Caesar
He, along with others, reportedly smuggled about 55,000 digital images of some 11,000 dead detainees out of Syria.
Continue reading the main story Source of roughly half of the 55,000 imagesMilitary police photographer who worked for the government for 13 years Since uprising of March 2011, his job was to photograph bodies of detainees believed to have died under torture "Significant number" of bodies show signs of starvation, other injuries include burns, bruising, gouged eyes, ligature marks indicating strangulation, and signs of electrocutionSent images to relative by marriage outside Syria"Caesar" and family smuggled out after he feared for his safety and amid psychological strain of workHe said his job had been to take photographs of corpses, both to allow a death certificate to be produced and to confirm that execution orders had been carried out.He did not claim to have witnessed killings or torture himself.
The photographs in the report cover the period from the start of the uprising in March 2011 until August last year.
All but one of the bodies shown are male. Some had no eyes, and some showed signs of electrocution.
Syria's Justice Ministry dismissed the photos and accompanying report as "lacking objectiveness and professionalism", according to the Associated Press.
But one of the authors of the report, former Sierra Leone Special Court prosecutor David Crane, said the photographs - and the witness himself - were "credible and sustainable in a court of law".
While Caesar's photos would appear to offer evidence of war crimes by the Syrian government, both Mr Araud and Mr Crane said that crimes had also been committed by opposition forces.
More than 150,000 people have been killed since the conflict began, with millions forced to flee their homes.
The Syrian army has been fighting to contain protests in cities across the country Syrian forces have crossed into Lebanese territory and shot dead a Syrian man living in a border area, reports say.The man killed was reportedly a farmer living in a remote area of Lebanon's eastern Beqaa region. It was not clear why he was targeted.
It follows an incursion by Syrian tanks earlier this week, raising fears that Syria's unrest is spreading.
Some 5,000 Syrians have sought refuge in Lebanon in recent months.
They include deserting soldiers and opposition members fleeing a crackdown on protesters by the Syrian government.
At least 2,900 people have died in Syria since the uprising against the rule of President Bashar al-Assad began in March.
Porous borderAccording to reports, Syrian army vehicles crossed the border near Saaba, in the Beqaa region, and attacked farmers and their homes.
Witnesses said several buildings were damaged.
A Lebanese official told AFP news agency as saying the body of the Syrian man who died was left lying at the site, and that an investigation was under way.
It is unclear why the man, named as Ali al-Khatib - who was married to a Lebanese woman and living in the area - was targeted.
The BBC's Jim Muir in Beirut says the border near the Beqaa region is porous and not even clearly defined.
Lebanon has taken in several thousand Syrians fleeing the trouble in their own country.
Lebanese Prime Minister Najib Miqati has said they are being looked after on humanitarian grounds, but our correspondent says there have been reports of activists being hunted down and sent back to Syria.
Many protesters are calling for the overthrow of President Assad The death toll in Syria has risen to more than 2,900 people since the pro-democracy protests began in March, the United Nations human rights office has said. The UN had previously put the death toll at 2,700.
On Tuesday, the UN Security Council failed to agree a resolution on taking action against Syria.
Opposition activists said 16 people died in different parts of the country on Wednesday as protests continued.
President Bashar al-Assad has cracked down on them, blaming the unrest on "terrorists and armed gangs".
But he announced that local elections would be held in December.
Correspondents say this is unlikely to be acceptable to the protesters.
Many of them have stopped calling for reform, and are instead insisting on the overthrow of Mr Assad.
Propaganda victoriesAs activist networks reported more clashes on Thursday between forces loyal to the Syrian president and army defectors, videos surfaced of protesters burning Russian and Chinese flags - a reaction to the two countries' veto of the UN Security Council resolution on Syria.
A spokesman for the UN human rights office, Rupert Colville, said of the latest death toll that the names of the dead had all been confirmed and could include some members of the security forces.
He said the figures did not include those who had disappeared or remained unaccounted for.
The announcement came a day before the UN Human Rights Council in Geneva reviews Syria's record.
Meanwhile the BBC's Jim Muir, who is monitoring events in Syria from neighbouring Lebanon, says the government in Damascus is celebrating two big propaganda victories.
The state-run Syrian media are still playing up Russia and China's veto, with top officials clearly delighted, calling it a "historic" development dealing a blow to Western schemes for intervening in the country's internal affairs, our correspondent says.
Syrian state TV is also gleefully dwelling on the case of Zainab al-Hosni, the 18-year-old girl from Homs who was reported by her family and by human rights organisations to have been detained, beheaded and mutilated, he adds. She later appeared on Syrian TV to say she was alive and well.
The Syrian town of Deraa has been the focus of much of the protests The UK is working with its European partners on targeted sanctions against members of the Syrian regime, Foreign Secretary William Hague has said. He told MPs they were discussing "asset freezes and travel bans".
The EU has agreed an arms embargo against Syria, but France has said it wants President Bashar al-Assad to be targeted directly.
Activists say 560 people have been killed across the country in anti-government protests.
Speaking in the Commons, Mr Hague said the UK was at the "forefront of pressing for action by the EU".
"We are now working with our European partners on targeted sanctions on asset freezes and travel bans. I will be discussing this further with the French foreign minister this evening.
"We are also highly active at the United Nations Security Council," he said.
He also criticised the crackdowns by governments across the Middle East, saying: "Nothing can justify the use of lethal force against peaceful demonstrators."