U.S. warplanes launched airstrikes on what U.S. officials said was a gathering of Islamic State commanders near the militant-held city of Mosul on Friday, in one of the most prominent assaults on the Islamist group’s leadership since the air war started here in August.

A spokesman for U.S. Central Command could not confirm whether Islamic State leader Abu Bakr al-Baghdadi was at the gathering targeted on Friday. The strikes destroyed a convoy of 10 armed trucks, the spokesman, Col. Patrick Ryder, said. According to CENTCOM, the vehicles appeared to be pickups with gun mounts.

“We cannot confirm if ISIL leader Abu Bakr al-Baghdadi was among those present” in the convoy destroyed near Mosul, Ryder said, using an alternative acronym for the Islamic State.

Mosul, a city of roughly 1.5 million people, was seized by Islamic State militants in June. Baghdadi declared an Islamic caliphate from that northern Iraqi city in his first appearance as the group’s leader on July 5. Their military victory in Mosul granted the Islamic State command over one of Iraq’s largest cities, where they have imposed a strict version of sharia law on the local population, residents say.

Baghdadi, an Iraqi born in Samarra, is said to have been working as an Islamic preacher when the United States invaded Iraq in 2003. He then turned to militancy and was detained by U.S. forces at Camp Bucca for less than a year, according to Defense Department officials.

It was there that Baghdadi is believed to have met and trained with al-Qaeda operatives, eventually rising to lead the Islamic State. His militant group controls vast tracts of land that straddle the border between Iraq and Syria.

Also Friday, U.S. warplanes struck several targets in Iraq’s western Anbar province, Ryder said. Several of the strikes, near al-Qaim at the Syrian border, destroyed an Islamic State vehicle and several checkpoints, he said.

On Saturday, Iraqi government officials and tribal chiefs in Anbar reported fresh U.S. airstrikes near al-Qaim that they said also targeted and killed some of Baghdadi’s top aides. The raids could not be confirmed.

The Islamic State militants have overrun large areas of Anbar in recent weeks and control a majority of the province. Anbar was the epicenter of the Sunni insurgency against U.S. troops during the Iraq war, but local tribal leaders eventually turned against the extremists.

Those same Sunni tribesmen are requesting U.S. assistance to beat back Islamic State advances in Anbar, where the Islamist militants have massacred members of tribes resisting their rule. Since late October, the Islamic State has executed hundreds of members of the Albu Nimr tribe in Anbar, tribal leaders said. The Obama administration Friday authorized the deployment of an additional 1,500 troops to Iraq, including trainers and advisers who will specifically deploy to Anbar province.

The difficulty of determining who may have been killed in the weekend strikes reflects one of the many challenges the Obama administration faces as it extends its air campaign in Iraq while limiting the number of U.S. personnel on the ground.

While the United States has sophisticated systems to collect intelligence from the air, its small military footprint makes it harder to determine the outcome of air raids. That is even more true of U.S. strikes in Syria, where there is no American military presence.

The limited U.S. footprint in Iraq also poses challenges for other important tasks, such as assessing the abilities of Iraqi security forces. U.S. officials say Iraqi forces must lead the fight against militants even as they prepare to send additional American troops to retrain nine brigades of the Iraqi army, whose shortcomings were laid bare by the Islamic State’s success this summer.

But U.S. officials say that three months of steady strikes against the Islamic State in Iraq has prompted the group to alter its tactics, forcing the militants to move in smaller numbers and constraining their ability to communicate and plan attacks.

While the number of American troops would roughly double if Congress approves funding for Obama’s force expansion, the White House has pledged that no U.S. soldiers will take part in combat in Iraq.

Correction: An earlier version of this report incorrectly said that Islamic State leader Abu Bakr al-Baghdadi was detained by U.S. forces at Camp Bucca, in Iraq, for four years. Defense Department officials said Sunday that he was detained there for less than a year.

Missy Ryan in Washington and Mustafa Salim in Baghdad contributed to this report.