The US said Friday it carried out an air strike in Syria against an Al-Qaeda meeting but denied hitting a mosque where a monitor said 49 people were killed.
The Syrian Observatory for Human Rights said most of the dead in the late Thursday 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 containing "dozens" of Al-Qaeda members, "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.
Another Pentagon spokesman later said: "Intelligence indicated that Al-Qaeda leaders used this partially constructed community meeting hall as a gathering place, and as a place to educate and indoctrinate Al-Qaeda fighters."
An AFP correspondent who visited the area Friday said there are two Omar bin al-Khattab mosques in Al-Jineh, adjacent to each other. The old one was damaged and the new one totally destroyed.
Rescue workers in white helmets were still hoping to dig people out of the rubble, and managed to extract the body of a man.
Dusty Korans lay on the ground, the correspondent said.
US warplanes have 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 Friday it would "look into any allegations of civilian casualties in relation to this strike", which was carried out unilaterally by the United States.
- Some bodies 'unrecognisable' -
Saleh Saeed al-Sheikh, whose brother Mustafa was killed in the air strike, said there was a Koranic school inside the mosque.
Much of the building, identified outside by a black placard as a mosque, had been flattened.
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 on Thursday, adding that many were still trapped under the collapsed mosque in the village some 30 kilometres (20 miles) west of Aleppo.
Al-Jineh is held by Islamist groups, but the Observatory said no jihadist factions are present.
Resident Abu Muhammed 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 said.
- Syria says shot Israeli jets -
The strike was condemned by Islamist group Ahrar al-Sham, which said targeting mosques was a war crime under international law.
More than 320,000 people have been killed in Syria since the conflict began with anti-government protests six years ago.
A ceasefire between government forces and non-jihadist rebel groups was brokered by rebel backer Turkey and regime ally Russia in December, but violence has continued.
The skies over Aleppo province are busy, with Syrian regime and Russian warplanes as well as US-led coalition aircraft carrying out strikes.
Russia began a military intervention in Syria in September 2015, and in the past has dismissed allegations of civilian deaths in its attacks.
The US-led coalition said earlier this month that its raids in Iraq and Syria had unintentionally killed at least 220 civilians since 2014.
Critics say the real number is much higher.
Israel also carried out pre-dawn air strikes in Syria, hitting several targets near the famed desert city of Palmyra which prompted Damascus regime forces to retaliate.
The Syrian army said it had downed one Israeli plane and hit another, but Israel's military insisted the safety of its aircraft had not been compromised.
Israel said it intercepted one missile. Jordanian military sources said missile shrapnel hit the north of the kingdom without causing any casualties.
Israeli Prime Minister Benjamin Netanyahu said the strikes -- the most serious incident between the two countries since the Syrian civil war started in 2011 -- targeted "advanced" weapons bound for Hezbollah.
The Lebanese Shiite movement fought a devastating war with Israel in 2006 and is now fighting alongside the Syrian government.