2 U.S. advisers killed in Afghanistan

KABUL -- A gunman killed two ranking American military advisers with shots to the back of the head Saturday inside a heavily guarded ministry building, and NATO ordered military workers out of Afghan ministries as protests raged for a fifth day over the burning of copies of the Quran at a U.S. military base.

The Taliban claimed responsibility for the Interior Ministry attack, saying it was retaliation for the Quran burnings, after two officers -- a lieutenant colonel and a major -- were found dead on the floor of an office that only people who know a numerical combination can get into, Afghan and Western officials said.

The top commander of U.S. and NATO forces recalled all international military personnel from the ministries, an unprecedented action in the decade-long war that highlights the growing friction between Afghans and their foreign partners at a critical juncture in the war.

The U.S.-led coalition is trying to mentor and strengthen Afghan security forces so they can lead the fight against the Taliban and foreign troops can go home. That mission, however, requires a measure of trust at a time when anti-Western sentiment is at an all-time high.

Afghan Defense Minister Gen. Abdul Rahim Wardak called Defense Secretary Leon Panetta to apologize for the shooting and offer his condolences, Pentagon press secretary George Little said in a statement released in Washington.

"This act is unacceptable and the United States condemns it in the strongest possible terms," Little said.

Security is tight in the capital, which is covered in snow, and foreigners working at the U.S. Embassy and at international organizations have been banned from leaving their compounds.

U.S. officials said they were searching for the assailant, who has not been identified by name or nationality.

The two American officers were found by another foreigner who entered the room, according to the Afghan official, who spoke on condition of anonymity because he was not authorized to disclose details about the shootings. They were shot in the back of the head, according to Western officials, who spoke on condition of anonymity because they were not authorized to disclose the information.

Authorities were poring over security camera video for clues, the Afghan official said.

At least 28 people have been killed and hundreds wounded since Tuesday, when it first emerged that a few Qurans and other religious material had been thrown into a fire pit used to burn garbage at Bagram Air Field, a large U.S. base north of Kabul.

President Barack Obama and other U.S. officials have apologized for what they said was a mistake, but their regrets have not quelled the deadly protests.