Here are some of the main events in the uprising in Syria:
March 15, 2011 - About 40 people join a protest in Old Damascus, chanting political slogans in a brief first challenge to the ruling Baath Party.
March 18 - Security forces kill three protesters in southern Deraa, residents say. They were demanding political freedoms and an end to corruption.
March 22 - Hundreds of people march in Deraa and Nawa demanding freedom in the fifth straight day of demonstrations.
March 24 - President Bashar al-Assad orders the formation of a committee to study scrapping the emergency law in place for the last 48 years. The emergency law is lifted on April 19.
March 25 - There are reports of 23 deaths at marches around Syria, including, for the first time, in Damascus.
July 31 - Syrian tanks storm Hama, residents say, after a month-long siege. At least 80 people are killed.
Sept. 15 - Opposition activists announce a Syrian National Council to provide an alternative to the government.
Nov. 12 - The Arab League suspends Syria.
Dec. 19 - Syria signs Arab League peace plan.
Dec. 23 - Two suicide bombs target security buildings in Damascus, killing 44 people. Syria blames al Qaeda. The opposition blames the government.
Feb. 4, 2012 - Russia and China veto a resolution in U.N. Security Council, backed by Arab League, calling for Assad to step down. The General Assembly approves a resolution on Feb. 16 endorsing the Arab League plan calling for Assad to step aside.
Feb. 22 - More than 80 people are killed in Homs including two foreign journalists. Hundreds of people have been killed in daily bombardments of the city by Assad's forces.
Feb. 23 - Former U.N. Secretary-General Kofi Annan is appointed United Nations-Arab League envoy to Syria.
Feb. 24 - Foreign ministers from more than 50 countries meet in Tunis for the inaugural "Friends of Syria" meeting. Russia and China, allies of Syria, do not attend.
Feb. 28 - Assad decrees that a new constitution is in force after officials say nearly 90 percent of voters endorsed it in a Feb. 26 referendum. Opponents and the West dismiss it as a sham.
March 1 - Syrian rebels pull out of the besieged Baba Amr district of Homs after more than three weeks of bombardment.
March 27 - Syria accepts the U.N.-sponsored peace plan.
April 12 - U.N.-backed ceasefire comes into effect. Four days later monitors start to monitor the ceasefire in Syria.
May 7 - Syria says voters turned out in large numbers for a parliamentary election which the opposition denounces as a sham.
May 10 - Annan condemns attacks in Damascus in which two bomb blasts kill 55 people. A week later, U.N. Secretary-General Ban Ki-moon says he believes al Qaeda was responsible. He also says 10,000 people have now been killed.
May 25 - At least 108 people are killed, including many children, in attacks in the region of Houla.
June 3 - In a rare address to parliament, Assad condemns the massacre in Houla.
June 5/6 - Troops and militiamen loyal to Assad are accused of killing at least 78 people at Mazraat al-Qubeir, near Hama.
June 6 - Assad names party stalwart Riyad Hijab to form a new government, signalling no political concessions.
June 12 - The uprising has grown into a full-scale civil war U.N. peacekeeping chief Herve Ladsous says. Four days later the violence forces U.N. observers to suspend operations.
June 22 - Syrian troops shoot down a Turkish warplane. Damascus says it was self-defence, Ankara calls it an "act of aggression".
June 26 - Assad says his country is "at war".
June 30 - World powers agree Syria should have a transitional government but appear at odds over Assad's role.
July 6 - "Friends of Syria" meet in Paris, agree to increase aid to Syrian rebels.
- Brigadier-General Manaf Tlas, who headed a unit of Syria's Republican Guard and was a long-time ally of Assad, defects.
July 11 - Nawaf al-Fares, Syria's ambassador to Iraq, defects and joins the opposition.
July 12 - Activists say about 220 people, mostly civilians, are killed in the Sunni Muslim village of Tremseh in the Hama region. They say pro-Assad militiamen stormed the village after it was bombarded by helicopter gunships and tanks.
July 13 - Annan says he is shocked by the news of "intense fighting, significant casualties and the confirmed use of heavy weaponry" in Tremseh.
(Reporting by David Cutler, London Editorial Reference Unit) (Reporting by David Cutler, London Editorial Reference Unit)