The Syrian Observatory for Human Rights said the dead included women and children and the death toll from the air strikes, which hit a camp for internally displaced people near the town of Sarmada, was likely to rise.
Footage shared on social media showed rescue workers putting out fires which still burned among charred tent frames, pitched in a muddy field. White smoke billowed from smoldering ashes, and a burned and bloodied torso could be seen in the footage.
"There were two aerial strikes that hit this makeshift camp for refugees who have taken refuge from fighting in southern Aleppo and Palmyra," said Abu Ibrahim al-Sarmadi, an activist from the nearby town of Atmeh who spoke to people near the camp.
Nidal Abdul Qader, an opposition civilian aid official who lives about 1 km (half a mile) from the camp, said around 50 tents and a school had burned down.
United Nations aid chief Stephen O’Brien said he was horrified and sickened by what had happened and called for an investigation.
The White House said the victims were innocent civilians who had fled their homes to escape violence.
Sarmada lies about 30 km (20 miles) west of Aleppo, where a cessation of hostilities brokered by Russia and the United States had brought a measure of relief on May 5.
