Timeline: Key moments in Syrian crisis
The following is a timeline of key events in the Syrian conflict.
Beginning with the start of the uprising in March 2011, it charts major attacks on government targets as well as the worst cases of killings of civilians.
Efforts by the members of the international community to influence and bring an end to the conflict are also mentioned.
Deraa/Damascus, March 2011
Demonstrators demanded the release of political prisoners, but some were shot dead by security forces, triggering unrest that gradually spread throughout the country.
Deraa/Damascus, 22 April 2011
The Syrian uprising, then a month old, experienced its bloodiest day so far on 22 April when 72 protesters were killed by security forces firing on crowds.
Many of the dead were in the southern village of Ezra, near Deraa and in a suburb of Damascus.
Jisr al-Shughour, 3-6 June 2011
In June 2011, the Syrian government announced that 120 security personnel had been killed in the north-western town of Jisr al-Shughour.
The figure may have been inflated but it was a major attack and, as the BBC's correspondent Jim Muir said at the time, it showed that the government was facing an armed uprising rather than mass peaceful protests.
Turkey, 3 October 2011
Opposition groups formed the Syrian National Council and pledge to overthrow President Bashar al-Assad.
12 November 2011
The Arab League voted to suspend Syria, accusing it of failing to implement an Arab peace plan, and imposed sanctions.
Jabal al-Zawiya, 19-20 December 2011
Villages in the area of Jabal al-Zawiya in Idlib province were the site of a massacre of army defectors.
Opposition activists said around 70 soldiers were mown down by machine-guns on 19 December after hundreds fled their positions between the villages of Kafrouaid and Kansafra. This was later backed up by eyewitnesses and a report by Human Rights Watch.
The London-based Syrian Observatory for Human Rights said a further 111 people - also mostly army defectors - were hunted down by the army and killed the next day in an "organised massacre".
Homs, February-March 2012
Syrian forces began shelling the restive city of Homs on 3 February, in what was to become a month-long bombardment.
Early reports talked of as many as 200 deaths, but one of the main activist groups later revised its confirmed number down to 55.
The BBC's Paul Wood, who was in Homs travelling with fighters from the Free Syrian Army, described a city under siege.
The bodies of 45 people, mostly women and children, were found in the Karm el-Zeytoun neighbourhood of Homs on 12 March.
New York, 21 March 2012
The UN Security Council backed UN-Arab League envoy Kofi Annan's peace plan to end all violence, provide humanitarian relief and secure a peaceful transition of power. The Syrian government accepted the plan six days later.
16 April 2012
The first UN observers, a group of just six, began their work to monitor the situation on the ground as part of the Annan peace plan. Their numbers increased to nearly 300 over the following weeks, but with violence continuing to escalate they suspended their operations on 16 June.
Damascus, 10 May 2012
The largest of a series of attacks blamed on suicide bombers in the capital, in which 55 people died after explosions outside the military intelligence building.
Many of the attacks have targeted security facilities. The government blames anti-regime forces and Islamist groups linked to al-Qaeda, but the opposition says the attacks are staged in an attempt to discredit them.
Houla, 25 May 2012
The village of Taldou, in the Houla region near Homs, witnessed one of the worst massacres in Syria's uprising.
UN observers confirmed that 108 people were killed, most of them women and children. Some had been killed by shell fire, but the majority had been shot at point-blank range or stabbed.
The government blamed terrorists, but survivors and human rights groups pointed the finger at the army and shabiha militiamen allied to the government.
6 July, 2012
Manaf Tlas, a general from a Sunni family close to the Assads, fled Syria, in the highest-level desertion of the regime so far. Two weeks later, he was confirmed to be in France.
Tremseh, 12 July 2012
There are conflicting reports from Syria about the deaths of dozens of people in Tremseh, a village in Hama province.
Opposition activists and witnesses said army tanks bombarded the village for several hours before pro-government militiamen swept in, shooting and stabbing victims at close range. They reported that as many as 220 people were killed, including a number of rebel fighters.
The Syrian government said at least 50 people were killed in Tremseh, but it blamed "armed terrorist groups".
Damascus, 18 July 2012
Defence Minister Daoud Rajiha and his deputy Assef Shawkat, President Assad's brother-in-law, are killed in a suicide attack during a high-level meeting at the national security headquarters, Syrian state TV says.
General Hassan Turkomani, an assistant to the vice-president, is also killed in the attack.
The interior minister and national security chief were said to be injured in the attack, which some analysts describe as a turning point in the fate of the Assad regime.
The rebel Free Syrian Army (FSA) and a jihadist group calling itself Lord of the Martyrs Brigade both said they were behind the bombing. Reports say the bomber was working as a bodyguard for members of the inner circle.