WASHINGTON (AP) — U.S. warplanes bombed an al-Qaida training camp in Syria, killing more than 100 militants, marking the second major U.S. counterterrorism strike in the final hours of Barack Obama's presidency, a defense official said Friday.

The Syria strike was carried out by one B-52 bomber and an undisclosed number of U.S. aerial drones, the official said. The official, who was not authorized to publicly announce the operation and so spoke on condition of anonymity, said it happened at about noon Washington time on Thursday, less than 24 hours after a combination of B-2 stealth bombers and drones struck two military camps in a remote part of Libya, killing 80 to 90 Islamic State militants.

Obama specifically authorized the Libya strike. It was not immediately clear whether the Syria strike required his direct approval.

The militants killed in the Syria attack were described by the official as "core" al-Qaida members, among a number who had moved to Syria early last year to establish a foothold. The U.S. defense official distinguished these militants from members of the group formerly known as the Nusra Front, which is an al-Qaida affiliate in Syria.

The al-Qaida training camp struck on Thursday is situated in Idlib province west of Aleppo, not far from the Turkish border, the official said, adding that the Pentagon believes no civilians were killed in the attack.