Syrian government forces have killed more than 500 civilians during a week of intense bombardment of a rebel enclave near Damascus, activists say.
The victims in the Eastern Ghouta include 121 children, says the Syrian Observatory for Human Rights, a UK-based group monitoring the conflict.
Syrian government forces backed by Russia have been pounding the area since last Sunday.
The UN Security Council is struggling to agree on a ceasefire resolution.
A vote has been delayed several times since Thursday, and was due to meet on Saturday.