An airstrike on a crowded market in a Syrian village controlled by the Islamic State group killed dozens of people on Tuesday, activists said.

Two activist-run monitoring groups, the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees, said the attack occurred in the village of Khansaa, in far eastern Syria near the Iraq border. Khansaa is held by the Islamic State militant group.

The Observatory said "dozens" were killed and wounded. Other activists gave estimates ranging from 30 to 75 people killed. Conflicting tolls are common in the chaotic aftermath of violent incidents in Syria.

One activist reached over Skype in the nearby provincial capital of Hassakeh said he was given the names of 70 people presumed killed in the strike, and said another 13 bodies were too badly burnt to be identified.

The activist, who goes by the name Siraj, said he obtained the list from wounded survivors who were rushed to a hospital in a nearby town. But he said the toll could be revised as activists interviewed more survivors.

It also was not immediately clear who conducted the airstrike, Siraj said.

Some wounded residents said it was a Syrian government airstrike using so-called barrel bombs, canisters packed with explosives that are usually dropped from helicopters. Such bombs cannot be precisely targeted, and activists say they have killed thousands of civilians.

Other residents said warplanes from the U.S.-led coalition battling the Islamic State fired missiles at the market, according to Siraj.

The Local Coordination Committees said it was a Syrian government airstrike.