Zahran Alloush, the chief of Jaysh al-Islam, a major armed rebel group operating in the suburbs of Damascus, was killed along with five aides in an airstrike near the Syrian capital, a monitoring group reported Friday.
The Syrian Observatory for Human Rights said a warplane targeted a meeting attended by Alloush and other leaders of Jaysh al-Islam (The Army of Islam) in the rebel-held area of Eastern Ghouta on the outskirts of Damascus.
There were contradictory reports about the time of Alloush's death.
The Britain-based Observatory cited a source as saying that Alloush was killed in a Thursday air raid and not Friday as previously said.
The strike was mounted while the leaders were discussing preparations for an attack on Syrian regime forces and allied fighters from the Lebanese Hezbollah movement.
The Syrian Army said in a statement that its planes carried out a "special aerial operation" in eastern Ghotta which led to the killing of the Saudi-backed "terrorist Zahran Alloush" and a number of members from "Faylaq al-Rahman and Ahrar al Sham," two groups with close links to Alloush.
The statement said that the raid destroyed the base, killing everyone inside.
Syrian media reported that the leader of Faylaq al-Rahman, Abdel Nasser Shumeir, was also killed in the same raid.
However, the opposition Syrian National Coalition, which mourned Alloush, denounced the killing and accused Russian planes of carrying out the attack.
"What is being carried out by the invading Russia forces only serves the interest of terrorism and the Islamic State, weakening the free army factions that confronted terrorism and undermined its foundations," a statement by the coalition read.
Russian airstrikes began on September 30 across Syria, targeting Islamic State (Daesh) militants.
The Syrian National Coalition statement said that the attack was meant to hinder or abort UN efforts to reach a political settlement in Syria.
Ousama Abu Zeid, legal adviser to the Free Syrian Army, had earlier told dpa that the warplanes were Russian and fired 20 rockets into the site of the meeting was taking place.
Speaking to Dubai-based Al Arabia TV, activist Yasser al-Doumani from Douma, where Alloush hails from, said the opposition leader was buried quietly late Friday.
Jaysh al-Islam announced late Friday that it had appointed Abu Hamam al-Bouydani, a deputy of Alloush, to replace the dead leader.
Jaysh al-Islam has strongholds in the two Damascus suburbs of Douma and eastern Ghoutta. The group was reportedly responsible for shelling the capital on several occasions.
Alloush's death was confirmed on Twitter by the head of Syria's opposition National Coalition, Khaled Khoja, who said: "Gouta's factions should work hand-in-hand to fill the voids and complement the mission."
According to activists based in Syria, Alloush was in a meeting of his group's top leadership in the Marj al-Sultan neighbourhood in eastern Ghouta when the strike took place.
His death comes as the regime and Hezbollah, backed by Russian warplanes, said they were carrying out a major operation to retake rebel-held eastern Ghouta.
Alloush's group mainly controls areas in eastern Ghouta and attended opposition talks two weeks ago in Riyadh to unite ranks for possible peace negotiations with the regime forces in Geneva.
"Like all respected military groups, the death of the leader will not stop their political or military work. We believe that the retaliation will be tough," Abu Zeid said.
Alloush focused on preventing the expansion of Islamic State militants in areas on the outskirts of Damascus.
In an interview this month with US website the Daily Beast, Alloush said: "We want to rid our country of all dictatorial and terrorist projects."
Alloush, who spent at least two years in Syrian prisons, was released in a general amnesty in June 2011, a few months after the Syrian revolution erupted.
By Weedah Hamzah and Ramadan Al-Fatash

Al Bawaba