The U.N. political chief is calling the Syrian government's airstrikes on the Damascus suburb of Douma that killed some 100 people a war crime.

Jeffrey Feltman told the U.N. Security Council on Wednesday that Sunday's attack "would be yet one more war crime for which those responsible must be held accountable."

The Douma attack was one of the deadliest since Syria's crisis began in March 2011.

The Security Council has not yet issued a statement on the attack but was expected to discuss it behind closed doors Wednesday.

Syria on Tuesday accused U.N. special envoy Staffan de Mistura of bias after he condemned the government air raids on Douma and called them "unacceptable under any circumstances."

The attack hit the main market during rush hour, when hundreds were out shopping.