Five assassinated military commanders of the Syrian revolution
Here are five of them:
On 25 December 2015, the commander of Jaysh al-Islam (Army of Islam) was killed in the village of Utaya, near the town of Douma in the Eastern Ghouta - a Damascus suburb - by what is believed to have been a Russian airstrike.
Alloush, born in Douma in 1970, formed the ultra-conservative rebel group Jaish al-Islam late in 2013, and fought fierce battles against Islamic State group (IS) militants and the Syrian regime.
He was criticised by Syrian activists when, under his command, Jaish al-Islam paraded captured Alawite civilians in cages in Eastern Ghouta, using them as human shields against air raids.
The US and Saudi Arabia ciriticised the killing of Alloush and Saudi Foreign Minister Adel al-Jubeir said on Tuesday that attempts to assassinate leaderships fighting IS "do not serve the peace process and (efforts) to achieve a political solution in Syria."
He was succeeded as leader of the group by Abu Hammam Bouwaidani.Colonel Hussein Harmoush
In June 2011, during the early stages of the Syrian Civil War, Colonel Hussein Harmoush made an online video in which he publicly broke with the regime of President Bashar al-Assad.
He called on other Syrian soldiers to defect and join a group of rebels he labeled the "Free Syrian Army."
This led to more similar videos cropping up on the Internet, in which other soldiers followed his lead.
Harmoush disappeared on August 29 from a refugee camp in Turkey. He told his family and a Syrian activist that he was going to meet with a Turkish security man.
On September 15, he suddenly appeared in a video "confession" broadcast on state-owned Syrian television in which he retracted all previous anti-regime sentiments.
Syrian opposition activists claim that the Turkish authorities handed him over to the Syrian regime and traded him for nine members of the PKK Kurdish militant group.
Since then, conflicting reports have emerged about Harmoush's fate. Some say he was tortured and killed by Assad's regime and others say he is still alive in Sednaya prison northeast of Damascus.
Abdul Qader Saleh
The military commander of Tawhid Brigade in Aleppo and one of its founders.
He died from wounds sustained in a Syrian regime airstrike on a rebel-held air base in Aleppo province in November 2013, during a meeting between him and other senior figures of the rebel group.
Saleh played a major role in driving regime forces out of the northern Aleppo countryside and some of the city's neighbourhoods. He remained loyal to the Syrian revolution and its principles.
Tawhid Brigade, an Islamic militant rebel group formed in July 2012, was estimated to have at least 10,000 fighters in 2013.
Following the death of Saleh, the Tawhid Brigade suffered internal divisions and many of its members defected to other rebel factions.
Many leading figures of Harakat Ahrar al-Sham al-Islamiyya (Islamic Movement of the Free Men of the Levant) were assassinated in one day.
On 9 September 2014, a bomb went off during a meeting of senior commanders of Ahrar al-Sham, killing more than two-dozen senior commanders of the group, including the leader of the movement, Hassan Abboud.
It was said that the bomb contained a poisonous gas, which killed everyone in the meeting hall.
Ahrar al-Sham fought against IS and the Syrian regime but it appears more likely that the attack was not executed by Assad's men, but by forces belonging to one of the opposition groups.
Colonel Yousef al-Jader
Also known as Abu Furat. He headed a tank brigade in the Syrian army, but defected after he refused to follow orders to target and bomb the city of al-Hiffa in the Latakia countryside.
He joined the Twahid Brigade and became the commander of its military operations in Aleppo where he led many battles.
Hours after he read a statement announcing the "liberation" of the Infantry School in Aleppo, he was killed when he confronted remnants of the Syrian regime forces inside the school in December, 2012.