UPDATE | American, Italian hostages killed in US drone strike

WASHINGTON (AP) — An American and an Italian held hostage by al-Qaida, as well as two Americans working with the terror group, were inadvertently killed by U.S. drone strikes earlier this year, the government revealed today.

President Barack Obama said he took "full responsibility" for the counterterror missions and offered his "grief and condolences" to the families of the hostages.

Obama defended the legality of the January drone strike that killed the hostages and said there had been no evidence that the two men were present at what the U.S. had determined was an al-Qaida compound.

"Based on the intelligence that we had obtained at the time, including hundreds of hours of surveillance, we believed that this was an al-Qaida compound, that no civilians were present and that capturing these terrorists was not possible," Obama said at the White House. "And we do believe that the operation did take out dangerous members of al-Qaida."

Among those believed killed in the strike was Ahmed Farouq, who the White House said was an American who was an al-Qaida leader. U.S. officials have also concluded that Adam Gadahn, an American who had served as a spokesman for the terror network, was killed in a separate operation in January.