Damascus: Regime air raids killed almost 100 people, many of them civilians, in rebel-held Douma near Syria`s capital, in carnage coinciding with a visit to the war-torn country by the UN humanitarian chief.
Since a revolt against President Bashar al-Assad erupted in mid-March 2011, such attacks have multiplied.
Hundreds of people have been killed -- and on one occasion more than 1,500 -- under similar circumstances.
Here is a rundown of the deadliest attacks against rebels and civilians in Syria.
-- 2012 --
- February 4: The opposition Syrian National Council (SNC) reports a massacre in the central city of Homs, with more than 230 civilians killed in a single night by regime forces firing tank and mortar shells. The government denies the charge.
- May 25: At least 110 people are massacred near the central town of Houla, the United Nations says. A probe determines that pro-regime forces are responsible.
- June 6: Pro-Assad forces kill at least 55 people, including many women and children, in Al-Kubeir, Hama province, the SNC charges.
- July 12: Shelling and fighting on the ground kill more than 150 people, including dozens of rebels, in the central town of Treimsa, also in Hama, the Syrian Observatory for Human Rights reports. It says some of them were summarily executed.
- December 23: More than 60 people are killed in a regime air strike on customers lined up near a bakery in the rebel-held town of Halfaya, the Observatory says. Human Rights Watch (HRW) had warned that the regime had taken to targeting bakeries in the northern province of Aleppo.
-- 2013 --
- January 15: Twin blasts kill more than 80 people, mainly students, at the university in Aleppo, the second biggest Syrian city. Assad`s regime and rebels blame each other for the carnage.
- May 2-3: Regime forces execute at least 248 people in the majority Sunni coastal villages of Bayda and Banias, HRW says.
- August 21: Chemical weapons attacks blamed on the regime on two rebel-held areas near Damascus kill more than 1,500 people, according to the United States, which threatens punitive strikes before backing down following a Russian initiative to destroy Syria`s chemical arsenal.
-- 2014 --
- February 1: Barrel bombs dropped from army helicopters and planes kill at least 85 people in rebel-held districts of Aleppo, the Observatory says.
A series of previous raids there in December had killed 76 people, including 28 children.
- November 25: At least 95 people, including 52 civilians, die in air strikes against Raqa, a stronghold of the Islamic State jihadist group northeast of Damascus.
-- 2015 --
- February 5: A wave of around 60 regime air strikes on the opposition-held Eastern Ghouta area near Damascus kills 82 people after a barrage of opposition fire hits the capital, the Observatory says.
- August 16: A series of air strikes on a crowded market in Douma, in Eastern Ghouta northeast of Damascus, kills 96 people, "horrifying" visiting UN humanitarian chief Stephen O`Brien.
In four years of conflict between regime, rebel, Islamist and Kurdish forces, a total of more than 240,000 people have been killed, according to Observatory figures.