Suspected Russian jets killed at least 20 people and wounded dozens early on Thursday when they dropped bombs on two residential buildings in a besieged rebel enclave east of the Syrian capital, residents and a war monitor said.

At least four bombs flattened the buildings in the town of Misraba, wounding more than 40 people, they said, while at least ten people were killed in aerial strikes in nearby towns in the last rebel stronghold near the capital, reported Reuters.

The Syrian Observatory for Human Rights, a war monitor based in Britain, said 11 women and a child were among the dead in the strike in Misraba.

Video footage downloaded by activists on social media showed rescue workers pulling women and children from the rubble. The footage could not be independently confirmed.

Backed by Russian strikes, government forces have escalated military operations against Eastern Ghouta in recent months, seeking to tighten a siege that residents and aid workers say is a deliberate use of starvation as a weapon of war, a charge the government denies.

The rebel assault aims partly to relieve that pressure.

Jets have pounded rebel-held Harasta when rebels this week overran a major base in the heart of the enclave which residents say the army uses to pound residential areas.

The United Nations says about 400,00 civilians besieged in the region face “complete catastrophe” because aid deliveries by the government were blocked and hundreds of people who need urgent medical evacuation have not been allowed outside the enclave.

Russia rejects opposition and rights groups’ accusations that its jets have been responsible for deaths of thousands of civilians since its major intervention two years ago that turned the tide in favor of Syrian President Bashar al-Assad.

Scores of hospitals and civil defense centers have been bombed in what the opposition said is a “scorched earth policy” to paralyze life in rebel-held areas.

Moscow says it only attacks hardline Islamists.