Syrian troops launch an offensive in the suburbs of Damascus. The opposition accuses the army of chemical weapons strikes east and southwest of the capital, including one in Moadamiyet al-Sham that killed more than 1,300 people. The Syrian government denies the claims and the United Nations calls for a probe.
Videos posted on the Internet show medics attending to suffocating children and hospitals being overwhelmed.
International pressure mounts on the Syrian government to allow UN experts already in the country since August 18 to investigate the claims.
The United States mulls possible military strikes as Britain and France say the Syrian government was behind the August 21 gas attack.
Russia warns against military intervention without UN Security Council approval. Foreign Minister Sergei Lavrov says the West has no proof to back claims Syria's regime used chemical weapons.
A US intelligence report blames Syria's government for the attack with "high confidence" and says that 1,429 people were killed, including 426 children.
US President Barack Obama says he will ask the US Congress to authorize military action.
Lavrov calls on Damascus to hand over control of its chemical weapons arsenal to international supervision to head off military action. Syrian Foreign Minister Walid Muallem welcomes the call but the opposition dismisses it as a "political maneuver".
The UN formally accepts Syria's application to join the convention banning chemical weapons.
The United States and Russia agree on a plan to eliminate Syria's chemical weapons by the middle of 2014.
A UN reports says there is clear evidence that saran gas was used in the August 21 attack
The Hague-based Organization for the Prohibition of Chemical Weapons (OPCW) says Syria has handed over a complete inventory of its chemical arsenal, meeting a deadline to avert military strikes.
UN experts probe seven alleged chemical weapons attacks in Syria, including the August 21 attack and three subsequent ones. They aim to produce a comprehensive report by late October.
The UN Security Council unanimously passes a landmark resolution ordering the destruction of Syria's chemical weapons and condemning the August 21 attack.
OPCW team arrives in Damascus at start of disarmament mission.
Team members begin work on checking Syria's inventory of its arsenal.
OPCW team starts work on destroying the weapons and production facilities.