Six U.S. service members were killed in a suicide attack on a patrol near Bagram Air Base on Monday, CBS News correspondent David Martin reports. The attacker was on a motorbike.

The governor of Parwan province, Mohammad Asim Asim, said the eight-man foot patrol was rammed by the explosive-laden bike.

The attack occurred at approximately 1:30 p.m. local time. Bagram is the biggest U.S. military base in Afghanistan.

"We're deeply saddened by this loss," said Brig. Gen. Wilson A. Shoffner, Resolute Support Deputy Chief Of Staff For Communications. "On behalf of General Campbell and all of Resolute Support, our heartfelt sympathies go out to the families and friends of those affected in this tragic incident, especially during this holiday season."

NATO said the incident was under investigation.

A Taliban spokesperson claimed responsibility for the attack on Twitter, saying that approximately 20 U.S. soldiers had been killed.

This is the first major attack on a NATO military convoy since August 22, when three American contractors with the RS base were killed in a suicide attack on their convoy in Kabul. On August 7 and 8, Kabul was the scene of three insurgent attacks within 24 hours that left at least 35 people dead. One of the attacks, on the Qasaba U.S. special operations base outside Kabul left one soldier and eight civilian contractors dead.