4 Americans killed in blast at air base in Afghanistan

Afghanistan's National Army soldiers guard, blocking the main road to the Bagram Airfield's main gate in Bagram, north of Kabul, Afghanistan, Saturday, Nov. 12, 2016. An explosion at a U.S. airfield in Afghanistan early Saturday killed four people, the head of international forces in the country said. (AP Photos/Massoud Hossaini)
Afghanistan's National Army soldiers guard, blocking the main road to the Bagram Airfield's main gate in Bagram, north of Kabul, Afghanistan, Saturday, Nov. 12, 2016. An explosion at a U.S. airfield in Afghanistan early Saturday killed four people, the head of international forces in the country said. (AP Photos/Massoud Hossaini)

KABUL, Afghanistan (AP) — The U.S. military says four Americans have been killed in an explosion at the Bagram air field in Afghanistan.

Defense Secretary Ash Carter says two U.S. servicemen and two American contractors were killed. Another 16 U.S. service members and one Polish soldier were wounded.

The Taliban claimed responsibility for the attack, which they said was carried out by a suicide bomber inside the base. The Taliban regularly fire rockets at the base north of Kabul from outside its perimeter.

A spokesman for the governor of Parwan province, where the air field is based, told The Associated Press that laborers employed at the base usually line up at the gates around dawn and the attacker could have been among the men entering the base on Saturday.