The US said it carried out an air strike in Syria against an Al-Qaeda meeting but denied hitting a mosque where a monitor said today 46 people were killed.
The Syrian Observatory for Human Rights said most of the dead in last evening's raid on the village of Al-Jineh in the northern province of Aleppo were civilians.
In Washington, the Pentagon insisted a mosque was not hit but rather a nearby building with "dozens" of Al-Qaeda members inside, "several" of whom were killed.
"The mosque is still standing and relatively unscathed," Pentagon spokesman Navy Captain Jeff Davis said. "The building we targeted was adjacent" and the strike "clearly hit the intended target".
He showed a black-and-white image of what appeared to be an old mosque with a flattened building a short distance away.
Davis did not say what that destroyed building's purpose had been or whether it could have been somehow connected to the old mosque in Al-Jineh.
The US has been bombing jihadists in war-torn Syria as part of an international coalition since 2014, with hundreds of civilians unintentionally killed in the country and in neighbouring Iraq.
The US Central Command said today it would "look into any allegations of civilian casualties in relation to this strike", which was carried out unilaterally by the United States.
At the scene, an AFP correspondent saw rescue workers in white helmets working under spotlights with picks and shovels late yesterday to dig people out of the rubble.
Much of the building, identified by a black placard outside as a mosque, had been flattened.
The empty prayer hall was covered in debris, and rescue workers stepped through it carefully, discussing how to break down a wall to search for more survivors.
Fearing additional air strikes, weekly Friday Muslim prayers were cancelled in towns and villages across northern Syria, AFP's correspondent said.
Rescuers had earlier left the wreckage site but were forced to double back when they heard moaning come from the rubble.
"More than 100 people were wounded," Observatory head Rami Abdel Rahman said yesterday, adding that many were still trapped under the collapsed mosque in Al-Jineh, just over 30 kilometres west of Aleppo.
The village is held by Islamist groups, but the Observatory said no jihadist factions are present.
Abu Muhammed, a village resident, told AFP that he "heard powerful explosions when the mosque was hit. It was right after prayers at a time when there are usually religious lessons for men in it.
"I saw 15 bodies and lots of body parts in the debris when I arrived. We couldn't even recognise some of the bodies," he added.
The strike was condemned by Islamist group Ahrar al-Sham, which said targeting mosques was a war crime under international law.