Forty-two people have been killed and many more injured in an airstrike on a mosque in a rebel-held village of northern Syria, the Syrian Observatory for human rights has said.
The attack on Thursday is said to have taken place in al-Jina, near the province of Idlib in western Aleppo, a day after the sixth anniversary of the start of the country's civil war.
The area is home to hundreds of thousands of Syrians displaced by fighting.
American officials said US forces carried out an airstrike in Idlib on Thursday "killing several terrorists", but made no mention of civilian casualties.
"We did not target, not did we strike a mosque," Media Operations Chief Major Josh Jacques told ITV News.
"We targeted an Al Qaeda gathering across the street from a mosque.
He continued: "The mosque does not appear to be damaged following the strike. We are aware of the reports of civilian casualties and we are looking into it."
Meanwhile, the Syrian Civil Defence, volunteer paramedics known as the White Helmets, said three civilians were killed in an early morning airstrike on the village of Sheikh Ali in the Aleppo countryside.
The airstrike also came a day after suicide attacks in the capital, Damascus, killed at least 30 people.