A suicide attack in Afghanistan has killed six Americans on a joint NATO-Afghan patrol on Monday (local time) – the deadliest attack on international forces since August.
Two American troops and an Afghan were also wounded in the attack, in which an explosives-laden motorcycle rammed into the patrol.
Taliban fighters have overrun a strategic district in southern Helmand province, and US officials believe the insurgency is gaining strength in the region.
NATO and Afghan officials report the soldiers were targeted as they moved though a village close to Bagram Airfield – the largest US military base in Afghanistan.
The Taliban has claimed responsibility.
"Our heartfelt sympathies go out to the families and friends of those affected in this tragic incident, especially during this holiday season," says US Army Brig Gen William Shoffner, head of public affairs at NATO's Resolute Support base in Kabul.
US Secretary of Defence Ash Carter called the attack "a painful reminder of the dangers our troops face every day in Afghanistan".
The Taliban insurgency has intensified in the year since the international combat mission ended last year. Troops remain in the country training, assisting and advising their Afghan counterparts, who are fighting a battle-hardened Taliban force alone.
Helmand is a strategic province, as it produces the majority of the world's opium – used the help fund the insurgency.