BEIRUT (AP) — Syrian government shelling and airstrikes have killed nearly two dozen civilians in three days of fighting in the suburbs of the capital where rebels are trying to take over a military installation, activists and a monitoring group said Thursday.

The fighting in the opposition-held Eastern Ghouta outside Damascus is the latest in now regular breaches of a local truce brokered by Russia, Turkey and Iran, that came into force in August.

The Britain-based Syrian Observatory for Human Rights said 22 civilians have been killed, and more than 100 wounded. Syrian state media, meanwhile, said rebel shelling from the area killed six people and wounded 45 in the government-held capital.

Fighters from the rebel Ahrar al-Sham faction on Wednesday penetrated a military compound outside Harasta, a town in Eastern Ghouta, according to the activist-run Ghouta Media Center. Fighting over the facility was still underway Thursday, according to the Observatory's director, Rami Abdurrahman.

Pro-government forces lost 37 fighters, including nine officers, in the clashes; scores of rebels were also killed or wounded, the Observatory said.

Ahrar al-Sham's media arm published photos purporting to show several munitions caches it uncovered inside the compound.

An aid warehouse was damaged by the fighting, spoiling food stocks, the World Food Program said in a statement. It said WFP "condemns the destruction of humanitarian food supplies in Eastern Ghouta."

Activists believe the worsening humanitarian situation sparked the fighting. Eastern Ghouta has largely been cut off by a tight blockade by pro-government forces, despite the August "de-escalation" agreement that was supposed to allow humanitarian aid in. The government has authorized only a limited number of relief convoys into the area. The U.N. estimates there are 350,000 people trapped by the blockade.

In October, residents stormed a food warehouse amid reports of starvation among children. The Observatory said two children died from malnutrition during the last two months.

"My children are here and they are hungry," said activist Ahmad Khansour. "I'm ready to do something about it."

U.N.-hosted political talks between the Syrian government and the opposition are to resume in Geneva on Nov. 28. Separately, on Nov. 22, Saudi Arabia will host talks in Riyadh among opposition and rebel groups.

Anas al-Dimashqi, an Eastern Ghouta activist, said the rebels are fighting to strengthen their negotiating positions ahead of these meetings.