WASHINGTON: Six American troops were killed on Monday when a suicide bomber attacked their patrol near Bagram air base in Afghanistan, a US official told Reuters, speaking on the condition of anonymity.

NATO’s Resolute Support mission had earlier provided the number of service members killed but did not offer their nationality.

Three NATO troops were wounded in the attack, according to US Army Brig. Gen William Shoffner, head of public affairs at NATO’s Resolute Support base in the Afghan capital Kabul.

The Taliban claimed responsibility for the suicide bombing, which was the largest attack on foreign troops in Afghanistan since August.

Shoffner said it happened at around 1.30 p.m. local time in the vicinity of Bagram, the largest US military facility in Afghanistan.

Mohammad Asim Asim, governor of Parwan province, where Bagram is located, said that a suicide bomber rammed an explosives-laden motorcycle into the combined NATO-Afghan foot patrol as it moved through a village close to the base, which is 45 kilometers (28 miles) north of Kabul.

He also said that two Afghan police officers were wounded in the attack.

It 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 a US special operations forces base outside Kabul left one US soldier and eight Afghan civilian contractors dead.

Monday’s attack came as Taliban gunmen and government forces battled for control of a strategic district in the southern province of Helmand after it was overrun by Taliban insurgents, delivering a serious blow to government forces.

Mohammad Jan Rasulyar, Helmand’s deputy governor, said insurgents took control of Sangin district on Sunday. Only Afghan army facilities in the district had not been taken by the insurgents, he said. Casualties among Afghan security forces were high, he added, though he gave no figures.

Afghan Army commandos and special forces had arrived in Sangin to push a counter-offensive, the Defense Ministry spokesman, Dawlat Waziri, said. He told reporters the Afghan air force had conducted 160 combat and transport flights over Sangin in the past 48 hours.

Among the insurgent forces in Helmand, “three out of 10 are foreign fighters,” he said, adding that they included Pakistanis, Chechens, Uzbeks, Arabs and Chinese Uighurs. “The presence of the foreigners in this imposed war complicates the sitaution in Helmand,” he said, echoing the government line that the war is run by a Taliban leadership believed to be based in Pakistan with official protection.

Helmand is an important Taliban base as it produces most of the world’s opium, a crop that helps fund the insurgency.