Outside observers said the attacks, which Pentagon officials said struck 22 targets overall, killed at least 120 jihadi fighters, including at least 70 who were associated with the Islamic State and another 50 who belonged to the al-Qaida-affiliated Nusra Front and who were apparently killed in U.S. missile attacks aimed at Nusra's Khorasan unit, which U.S. officials said was plotting an imminent attack on the West.

 But Syrian rebels and media activists said the airstrikes also killed at least 10 civilians when a missile struck a building temporarily housing displaced people in Idlib province. They said that the Islamic State had evacuated many of the buildings and encampments struck in Raqqa, the Islamic State's de facto capital.

Activists in another town hit in the U.S.-led offensive, Ash Shadadi, said all of the Islamic State's bases were empty when bombed.