The U.N. Security Council met for urgent talks on Sunday as Syrian and Russian warplanes pounded rebel-held east Aleppo in the worst surge of bombing to hit the devastated city in years.
Britain, France and the United States called the emergency meeting to turn up pressure on Russia and press demands that it rein in its ally Syria to halt the intense bombing campaign on Aleppo.
"War crimes are being committed here in Aleppo," French Ambassador Francois Delattre told reporters, adding: "They must not be unpunished and impunity is simply not an option in Syria."
"Just when we thought things couldn't get any worse in Syria, they have," British Ambassador Matthew Rycroft said.
"The incendiary munitions that are dropping on Aleppo are indiscriminate and a clear breach of international law -- the barrel-busting bombs that are falling from the skies likewise," he said.