At least 49 people were killed in the airstrike that the US military said targeted al-Qaeda militants. Rebels and a monitoring group said the airstrike killed civilians at a mosque.
The Pentagon on Friday said it targeted an al-Qaeda meeting in northern Syria but denied hitting a nearby mosque as claimed by rebels and a monitoring group.
The UK-based Syrian Observatory for Human Rights said the airstrike late Thursday evening hit the Omar Ibn al-Khattab mosque compound in Jeeneh, north of Aleppo, killing at least 49 civilians and wounding dozens more.
A US Central Command spokesman said manned and unmanned aircraft did not target or strike a mosque.
"We targeted an al-Qaeda gathering across the street from a mosque. The mosque does not appear to be damaged following the strike," US Army Maj. Josh Jacques said.
Pentagon spokesman Jeff Davis later showed reporters an aerial surveillance image taken five minutes after the strike, showing the mosque still intact and a building across the street destroyed.
"The mosque is still standing and relatively unscathed," he said. "The building we targeted was adjacent" and the strike "clearly hit the intended target."
He said the airstrike's target was a meeting of senior al-Qaeda figures. He said that officials were still assessing the airstrike but that no civilians were believed to have been killed.
Another Pentagon spokesman later said the airstrike hit a "partially constructed community meeting hall" used by al-Qaeda.
The Syrian Observatory for Human Rights said both buildings were part of the mosque complex.
An AFP news agency correspondent visited the scene of the strike and said there were two Omar bin al-Khattab mosques, one of which was damaged while the other was flattened.
The powerful Ahrar al-Sham conservative rebel group blamed the United States for the airstrike, saying that "targeting mosques and places of worship is a war crime."
The US military said earlier this month that 220 civilians in Iraq and Syria had been killed unintentionally since 2014 in the course of an air campaign against the "Islamic State."
Critics and monitoring groups say the number of civilian deaths is much higher.
cw/sms (AFP, AP, Reuters)