Mediator Lakhdar Brahimi will meet representatives of the warring sides in Syria separately for the first few days to increase pressure on them.
State television has confirmed a helicopter crashed in Damascus but gave no details as Bashar al-Assad continues to bombard rebel-held districts.
More than 200 bodies have been found in basements and houses, and most were killed "execution-style" by troops on house-to-house raids.
Syrian Prime Minister Riyad Hijab is the latest to jump ship as defections continue to rattle Bashar al-Assad’s increasingly unstable regime.
Tanks have moved close to Aleppo but kept clear of new Turkish air defences installed to curb Syrian action near its frontiers.
Rebels are fighting security forces in Damascus in the most violent gun battles the Syrian capital has seen since the start of the year-long uprising.
Syria’s Al-Assad is arguably a war criminal, the US’s Hillary Clinton admitted, as the UN said his forces had killed more than 7 500 civilians.
Syrian forces shelled an opposition stronghold in Hama, killing 20 people, as two injured foreign journalists trapped in the city escaped to Lebanon.
The US appears open to arming Syria’s opposition, saying that if a political solution to the crisis was impossible, other options would be considered.
Syrian troops have attacked rebel strongholds in Dera’a where the uprising against President Bashar al-Assad erupted nearly a year ago.
No image available
/ 15 February 2012
No casualties from Syria’s offensive on the city of Hama have been made available as communication was cut off in the residential neighbourhood.
No image available
/ 18 January 2012
Fighting has subsided in a rebel-held Syrian town after a fragile ceasefire took hold between President Bashar al-Assad’s forces and insurgents.
At least a dozen Syrian secret police have defected from an intelligence compound, activists say, in what appears to be the first major desertion.
Syrian troops shelled two northern villages overnight after an attack by army defectors on forces loyal to President Bashar al-Assad.
Over 50 people have been killed in Syria ahead of Friday prayers as a seven-month crackdown on pro-democracy protests becomes more violent.
The UN says that despite an agreement to end the assault on Syrian rebels, troops loyal to Bashar al-Assad have continued the brutal crackdown.
Bashar al-Assad’s opponents have taken a step toward unity by forming a national council to represent Syria’s uprising but have a long way to go.
No image available
/ 9 September 2011
President Bashar al-Assad’s opponents broke a taboo by appealing for foreign help to stop the killing of civilians.
An armoured Syrian force surrounded a town near the city of Homs on Monday and fired heavy machineguns after the defection of soldiers in the area.
Syrian forces killed at least three protesters as tens of thousands of people marched again to demand the removal of President Bashar al-Assad.
Syrian forces have killed dozens of protesters despite assurances by President Bashar al-Assad to Ban Ki-moon that a crackdown was over.
Syrian tanks fired on low-income Sunni Muslim districts in the city of Latakia on Tuesday, the fourth day of an assault which has killed 36 people.
Syrian tanks and navy ships shelled the main Mediterranean port city of Latakia on Sunday, residents and rights groups said, killing at least 26.
Syrian tanks and navy ships have shelled Latakia, rights groups say, killing 24 people as President Bashar al-Assad’s forces try to quell protests.
Turkey demanded on Tuesday that Syria’s leaders stop the killing of civilians and said it would watch events there in the coming days.
Syrians began Ramadan in sombre mood on Monday after troops stormed into Hama in one of the bloodiest days of the five-month-old uprising.
Syrian army tanks stormed the city of Hama at dawn on Sunday, killing at least 24 civilians, residents said, after besieging it for nearly a month.
Syrian forces shot dead at least 11 people during mass protests on Friday against President Bashar al-Assad, rights activists and witnesses said.
Security forces shot dead at least 15 people on Friday after thousands took to the streets demanding the overthrow of President Bashar al-Assad.
Syrian troops have deployed on a main road leading from the commercial hub of Aleppo to Turkey as protests expand to border regions.
Syrian President Bashar al-Assad is to address the nation on Monday as his forces sweep through the north-western border region.
Syrian forces swept through a north-western border region on Sunday to stem an exodus of refugees to Turkey.