The leader of a powerful Syrian rebel group that controls key suburbs of Damascus was killed in an airstrike Friday, according to activists and local media.

Zahran Alloush, who headed Jaish al-Islam, was holding meetings with rebel officials when their compound near the Syrian capital came under attack, according to the Britain-based Syrian Observatory for Human Rights.

The death of Alloush, if confirmed, could have significant repercussions on the grinding battles taking place just beyond government-held Damascus in suburbs controlled by rebel forces. Jaish al-Islam holds sway over the vast Eastern Ghouta area east of the capital, preventing President Bashar al-Assad from consolidating territory that is just a few miles from his seat of power.

Reports of Alloush’s death also come amid intensifying diplomacy over the Syrian conflict, which has killed more than 250,000 people, displaced millions and emboldened extremist groups such as the Islamic State.

In a rare sign of unity over Syria, the U.N. Security Council adopted a resolution last week backing a peace process to end the civil war. That process aims to set into motion talks in Geneva between Assad’s government and the Syrian opposition that would create a timeline for drafting a new constitution and holding elections.

The renewed diplomacy has offered glimmers of hope for movement toward ending the conflict, bringing together Assad’s opponents, including the United States and Saudi Arabia, and his Russian and Iranian supporters.

On Friday, citing activists from the Local Coordination Committees, the Associated Press reported that Russian warplanes carried out the attack on Alloush.

Russia has shifted the momentum of the Syrian war since its military intervention in support of Assad in late September, but Moscow’s large-scale air campaign has not delivered dramatic results. Russia says its attacks are aimed at the Islamic State, but U.S. officials and activists say Moscow’s bombings have largely targeted rebel groups and killed scores of civilians. Rights groups have alleged indiscriminate use of cluster munitions by the Russians in their attacks.

The killing of Alloush, a controversial figure who helped turn Jaish al-Islam into one of the most organized and powerful rebel groups in Syria, may offer a morale boost to Assad’s beleaguered forces. State television said the bodies of Alloush and other rebel leaders were buried in the rubble after the airstrike, the Reuters news agency reported.

Alloush’s forces receive backing from Saudi Arabia, which has supported Syrian rebels but has thrown its weight behind the renewed diplomatic push to end the conflict. Intensified Russian strikes on rebel forces, including Saudi allies such as Alloush, however, may shake the oil-rich kingdom’s support for renewed peace efforts.

Alloush, who was in his mid-40s and had studied Islamic law in Saudi Arabia, was released from a Syrian prison in 2011 as part of an amnesty and then joined the revolt against the government.

His group defended an area that has faced repeated and indiscriminate air raids by the government. His forces, in turn, have fired indiscriminate mortar salvos at areas in Damascus, killing and wounding scores of civilians.

Although Alloush’s forces have battled extremist groups such as the Islamic State, Alloush also had issued statements that appeared sympathetic to al-Qaeda and its late leader, Osama bin Laden. Alloush also ruffled feathers with pejorative remarks about religious minorities in Syria, including the Alawite sect, an offshoot of Shiite Islam. The Assad family is Alawite.

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