Image copyright Getty Images Image caption The attack is one of the deadliest on American forces this year

A suicide bombing in Afghanistan has killed six US service members in one of the deadliest attacks on American forces this year, US officials say.

The Taliban said they were behind the blast, which also injured two US soldiers and a contractor.

US officials said the troops were meeting a local Afghan leader when they were targeted by a fighter riding a motorbike rigged with explosives.

Attacks on foreign troops have risen in recent months as forces have withdrawn.

Nato formally ended its combat operations last year, but 9,800 US troops remain in Afghanistan.

US Defence Secretary Ash Carter said the bombing was "a painful reminder of the dangers our troops face every day in Afghanistan".

The attack happened in a village close to Bagram airbase in Afghanistan.

To date, 16 US service members have been killed in combat this year, but most of those deaths were due to aircraft crashes, according to the Pentagon.

Image copyright Reuters Image caption The Taliban has claimed responsibility for the attack

In October, a helicopter crash killed six US service members in Jalalabad.

"We're deeply saddened by this loss," Brig Gen Wilson Shoffner said in a news release. "Our heartfelt sympathies go out to the families and friends of those affected in this tragic incident, especially during this holiday season."

The incident is under investigation, according to the release.

In southern Afghanistan, reports suggest that Taliban militants are getting close to taking Sangin, a strategically important town.

The Taliban have said they controlled most of the town, with the main administrative building abandoned.

The attack comes after US President Barack Obama has reversed his policy in Afghanistan, announcing that up to 10,000 service members will remain in Afghanistan by the end of his presidency.

Three Afghan police were also wounded in the bombing.

A few days ago, there were suicide attacks on the Kandahar air base in southern Afghanistan, and on a Spanish embassy property in Kabul.