The Pentagon on Friday denied accusations by a Syrian rebel group that the United States had targeted a mosque in Syria and, in a rare move, showed an aerial image to illustrate the mosque was intact and the building destroyed was in fact across the street.

Pentagon spokesman Captain Jeff Davis, addressing a Pentagon news conference, said he believed dozens of al Qaeda fighters were killed in the Thursday strike by manned and unmanned U.S. aircraft on an al Qaeda meeting place in the village of al-Jina, Aleppo.

Davis said the U.S. military had not yet seen any credible allegations of civilian casualties, including on social media.

The Pentagon released to the public the image it showed to reporters: a black and white aerial image showing the mosque still standing across the street from a building that had been reduced to rubble by the strike.

Next to the charred plot where the al Qaeda militants had met was another building, which was also still intact.

"We struck a meeting of senior al Qaeda terrorists, some of these were likely high value individuals, we're currently assessing that," Davis said.

But the Syrian Observatory for Human Rights, a Britain-based war monitoring group, said both buildings together make up the mosque.

The air strikes hit the mosque complex, which consists of a center belonging to an Islamist organization and a nearby prayer area, destroying the religious center, it said.

The Observatory said the strikes had killed at least 49 people and wounded dozens, mostly civilians who were attending a prayer and religious lesson at the center.

In a statement following the new conference, the Pentagon said intelligence indicated that the building that was struck was a "partially constructed community meeting hall" that was used by al Qaeda leaders "as a place to educate and indoctrinate" militants.

The statement said surveillance showed that the strike took place after evening prayers had finished.

It added that the image shown to reporters was taken less five minutes after the strike.

Reuters was unable to independently verify whether the mosque may have suffered any structural damage that could be difficult to see from an aerial image.

Ahrar al-Sham, a powerful Syrian rebel group, on Friday said the U.S.-led coalition against Islamic State was behind a deadly mosque attack near Syria's Aleppo that a war monitor said killed dozens of people.

The Observatory said jets hit around a mosque in al-Jina village near Atarib in the western part of Aleppo province, a few miles (km) from Idlib province on Thursday.

The United States has been leading a coalition in an air campaign against Islamic State while also carrying out air strikes against al Qaeda in Syria, which it says sought to take advantage of the chaos from Syria's civil war to reconstitute itself in ungoverned towns.

Syrian military and Russian jets have also carried out numerous air strikes against targets in Idlib and western parts of Aleppo province, which are held by rebels seeking to oust President Bashar al-Assad.

There are concerns about an increased risk of civilian casualties as U.S. President Donald Trump considers options to accelerate the fight against Islamic State militants in Iraq and Syria.

According to the U.S. military, 220 civilians killed have been killed since the start of the air campaign against Islamic State in 2014, but that estimate is far lower than those provided by monitoring groups.