The death toll for five days of bombardment by the Syrian regime and its allies on the rebel-held enclave of Eastern Ghouta passed the 400 mark Thursday, a monitor said.
"Five days of air strikes and intense artillery fire by the regime and its Russian ally have killed 403 civilians, including 95 children," the Syrian Observatory for Human Rights said.
The head of the Britain-based Observatory, Rami Abdel Rahman, said 46 people were killed in strikes and rocket fire on Thursday.
Bodies of victims killed earlier in the week were also retrieved from the wreckage of destroyed buildings, bringing the overall death toll to 403.
The regime, which is supported by Russian forces, intensified its operations against the enclave near Damascus on Sunday.
The area is controlled by militant groups but many civilian areas and even hospitals were targeted this week, sparking an international outcry.
The armed groups in Ghouta have also fired rockets and mortar rounds on civilian areas in the capital, which is under government control, killing at least 16 over the same period.