An airstrike on a crowded market in the northern city of Aleppo in Syria killed at least 21 people on Saturday. Many more were reported wounded.
The Syrian Observatory for Human Rights in London said the vegetable market was packed with morning shoppers when it was attacked at the time.
Videos showed extensive damage to the market and bodies being pulled from cars.
The BBC says government forces are reported to have killed about 400 people since attacks from the air began at Aleppo two weeks ago.
The air force is using barrel bombs - oil drums or cylinders packed with explosives and shrapnel.
The National Coalition said this week it would not attend a peace conference next month in Geneva if the air campaign continues.
Aleppo is the largest city and commercial capital of Syria.
The uprising in Syria began in March 2011 and has since become a civil war.