The U.S. military launched an airstrike at a building in northern Syria targeting what it says were senior Al Qaeda militants and is investigating reports that scores of civilians were killed or injured in the attack, the Pentagon said Friday.
Photos and videos on social media showed bloodied people emerging or being carried from a smoldering building in Aleppo province that local officials said was a mosque filled with worshipers at evening prayer.
The U.S. military insists dozens of militants were killed and denied bombing a mosque.
The Pentagon released a black-and-white aerial photo of a compound that it said showed a small mosque still standing. A much larger building across the road was reduced to rubble.
"We had tracked this building for some time," Capt. Jeff Davis, a Pentagon spokesman, said Friday. "We know it was being used by Al Qaeda, but at this particular time its purpose was to host this meeting of very senior people in Al Qaeda."
After the Pentagon released the photo, some Syrians said on social media that the building destroyed was a newly opened mosque and that the standing structure was an older place of worship.
The military is investigating whether civilians were inadvertently killed or injured, Davis added, but he said the photo showed the mosque was "relatively unscathed."
"As of the moment, we're not aware of any credible allegations of civilian casualties," he said.
The Syrian Observatory for Human Rights, a British-based monitoring group with a network of activists in Syria, reported Thursday that an airstrike hit the mosque in Al Jinah village and at least 42 people were killed. The group did not specify who launched the air attack.
"Some people [are] in critical situation and others are still missing," the group's report said, adding that the "search for missing, dead bodies and survivors under the rubble of the destruction caused by the bombing is still taking place."
Al Jazeera news agency reported that the attack occurred during "evening prayer so the mosque was full of worshipers, with local activists saying up to 300 people were inside at the time."
Syrian Civil Defense, a volunteer rescue group better known as the White Helmets, shared a video of searching for survivors in the rubble and injured people being loaded into ambulances.
The incident is the latest example of the gulf in reporting that exists between the Pentagon and Syrian human rights and humanitarian aid groups on the impact of deadly airstrikes.
Obtaining accurate independent figures is difficult because of the challenges of reporting on the ground in the multi-sided Syrian civil war.
The Pentagon estimates that at least 220 civilians have been killed in more than 18,900 airstrikes launched by the U.S. and its allies in Iraq and Syria since the air war against Islamic State began in mid-2014.
Independent monitoring groups say, however, that errant bombs or poor targeting have caused thousands of civilian casualties.
The U.S.-led coalition, Russia and Syria's government all conduct airstrikes against various militant groups in Syria in a civil war that has left hundreds of thousands of civilians, military and insurgents dead since 2011.
10:53 a.m.: This article was updated with new details.
7:30 a.m.: This article was updated with a figure for the number of airstrikes launched by the U.S. and its allies in Iraq and Syria since mid-2014.