A U.S. anti-terrorism operation in January killed American and Italian aid workers. White House officials said Thursday al-Qaida had been holding the two men on the Afghan-Pakistan border.

The victims, American Warren Weinstein and Italian Givovanni Lo Porto had been working on aid projects in Pakistan. A U.S. official told VOA the hostages were killed mistakenly during drone airstrikes January 14.

President Barack Obama on Thursday apologized for the incident.

He said, "As president and commander-in-chief, I take full responsibility for all our counterterrorism operations, including the ones that inadvertently took the lives of Warren and Giovanni. I profoundly regret what happened."