UPDATE 1:18 p.m.: Two senior defense officials have revealed that all six of those killed in the suicide bombing attack were from the U.S., marking the largest loss of U.S. life from an attack so far this year, according to USA Today. 

10:53 a.m.: Six coalition soldiers were killed and another three were injured Monday when a suicide bomber attacked a joint U.S.-Afghan patrol near Bagram Airbase in Afghanistan on Monday, NATO officials said.

"We're deeply saddened by this loss," said Brig. Gen. Wilson A. Shoffner, Resolute Support Deputy Chief of Staff for Communications, according to the Los Angeles Times. "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."

Governor of Parwan province, Mohammad Asim Asim, says the patrol was hit by an attacker on a motorbike laden with explosives, according to CBS News.

NATO could not immediately confirm the nationalities of the personnel killed in the attack, simply identifying those involved as foreign troops. However, an Afghan official later said that at least three U.S. service members were among the dead.

The Taliban have since claimed responsibility for the attack on Twitter as well as in an email to the Associated Press, reported CW's Chicago affiliate WGN-TV. However, per usual, they exaggerated the number of those killed, saying that 20 U.S. soldiers died in the attack.

In the meantime, NATO has launched an investigation into the attack.

The bombing follows reports that the Taliban had taken over the district of Sangin in the southern province of Helmand, which used to be the scene of heavy fighting between British forces and insurgents until 2010. U.S. Marines had taken responsibility of the area afterwards but they fully withdrew from Sangin in May 2014, leaving it ripe for the taking.