BEIRUT, Lebanon — At least 30 Syrian civilians were killed in an airstrike by the United States-led coalition fighting Islamic State militants in a rural area of Raqqa Province early Tuesday, according to residents, activists and state television.

The coalition said it had no indications that an airstrike hit civilians, but in its daily report on coalition strikes, the United States military acknowledged that strikes were carried out in the area. It said that coalition warplanes carried out 19 airstrikes on Tuesday — an unusually high number for a single day — on a range of Islamic State facilities near the city of Raqqa.

The attack, which hit a school in the town of Mansoura, where civilians had taken shelter on Tuesday night, was the second time in a week that Syrians had accused the United States of involvement in a strike that killed dozens of noncombatants.

Forty-nine people died last week when American warplanes fired on a target in Al Jinah, a village in western Aleppo Province. United States officials said the attack had hit a building where Qaeda operatives were meeting, but residents said the warplanes had struck a mosque where hundreds of people had gathered for a weekly religious meeting.