Kunduz, Afghanistan: Taliban militants in northeast Afghanistan killed 18 police in an ambush, the government said on Friday, as security forces struggle against the rebels with decreasing assistance from international troops.

The police convoy was caught in a firefight on Wednesday in the remote province of Badakhshan when officers were returning from an anti-insurgent operation.

The attack will heighten concerns that Afghan forces cannot provide effective security across the country, where a US-led invasion ousted the hardline Taliban regime in 2001, in time for the presidential election due in April.

“The acting interior minister is deeply saddened about the killing of 18 policemen and wounding of 13 others in a terrorist attack in Warduj district of Badakhshan,” a statement from the interior ministry said.

“A group of Afghan police forces on their return from a clean-up operation on the outskirts of Warduj district faced an enemy ambush and it resulted in the killing of brave Afghan policemen.”

Local officials confirmed the death toll to AFP.

The Taliban claimed responsibility for the attack in Afghanistan’s mountainous northeast, a region far from the insurgents’ southern heartlands and generally relatively peaceful.

Taliban militants killed 17 captured Afghan soldiers in the same district in March. The men were taken hostage while guarding a convoy.

Afghanistan’s 350,000-strong security forces are suffering a steep rise in casualties as the NATO combat mission winds down and Afghan authorities try to bring stability ahead of the presidential poll.

Last month 22 police were killed when hundreds of fighters ambushed a police and military convoy in the eastern province of Nangarhar.

The Afghan government declines to release exact figures, but the US department of defence has said that about 400 Afghan police officers and soldiers are killed in action every month.

When the 87,000-strong US-led military coalition fighting alongside Afghan forces withdraws by the end of next year, the ability of local troops to suppress the insurgents is seen as key to the country’s prospects.

The interior ministry added that 47 insurgents were killed and 20 others wounded in recent fighting in Warduj, which is on the approach to the Wakhan Corridor in the Himalayan mountains bordering Tajikistan, China and Pakistan.

The government this week claimed to have cleared all militants from the district.

Defence minister Bismillah Khan Mohammadi told the Tolo television news channel that the Taliban and other insurgent groups had all been “either killed or pushed out”.

The station reported that the militants’ presence and growing insecurity had forced some of Warduj’s few residents to flee their homes in past months.

On Thursday, a former Afghan lawmaker and district governor in the north said he had defected to the Taliban as the Islamists seek to strengthen their influence before the end of international combat operations.

Qazi Abdul Hai was a senator in the upper house of parliament for the province of Sar-e Pol between 2004 and 2008 and had also served as a district governor.

The insurgents have launched nationwide attacks during the current fighting season, but have made no territorial gains against Afghan security forces that have taken the lead in military operations since June.

NATO forces say they provide support to Afghan units when required, but do not plan or execute operations.