"Thirty-four civilians were killed in regime strikes and rockets on Eastern Ghouta," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, adding that 11 of the victims were children.

Rahman also said 26 of the people killed were in Ghouta's main town of Douma and its eastern suburb.

The regime's air strikes, artillery fire and rocket attacks on Ghouta over the past 15 days have left more than 690 civilians dead, according to SOHR.

Syrian President Bashar al-Assad said Sunday his forces must push on with their campaign to retake Eastern Ghouta from rebels, despite mounting international calls to end the bloodshed.

Assad's forces have seized over a quarter of the enclave on Damascus's eastern edges after two weeks of devastating bombardment, according to SOHR.

As the United States, Britain and France stepped up pressure on Damascus and Moscow to call off the assault, the United Nations said it plans to deliver much-needed humanitarian aid to Eastern Ghouta's residents.