Syrian activists say seven weeks of U.S.-led airstrikes have killed at least 860 people in Syria, most of them Islamic State militants.
The Britain-based Syrian Observatory for Human Rights said Wednesday the actual number could be much higher, and includes at least 50 civilians.
The U.S. and a coalition of other nations began hitting Islamic State targets in Syria in late September, expanding on an air campaign against the group in Iraq where the militants had seized large areas in the country's north and west.
A tally of statistics released by the U.S. Central Command shows coalition planes have carried out 350 airstrikes in Syria and another 450 in Iraq.
Several strikes have targeted the al-Qaida-linked Nusra Front. The Syrian Observatory, which has documented violence throughout Syria's civil war, said Wednesday that 68 Nusra members have died in those attacks.