Image copyright AFP Image caption Many police forces have come under attack from Taliban militants

Taliban fighters have seized the headquarters of a northern district in Afghanistan, officials say.

The militants captured the Kohistanat district in Sar-e-pul province after a night of heavy fighting.

It comes two days after the Taliban took control of a police base in northern Badakhshan province, capturing and later releasing over 100 officers.

Militant violence has increased since the departure of most US and Nato forces last year.

At least one local police commander in Kohistanat and several of his men had been forced to surrender to the Taliban, reports said.

Provincial police chief Gen Mohammad Aser Jabarkhail told AP news agency they had been unable to send police reinforcements in time because Kohistanat was too far away from the provincial capital.

Analysis: Waheed Massoud, BBC Afghan Service

The collapse and recapture of districts in Afghanistan's north is not unusual.

There are dozens of districts where the government now controls only the district centres, with the rest influenced by the Taliban. The total collapse of the district in Sar-e-Pul is important, but not a game changer.

Two years ago the general belief was that with the withdrawal of 150,000 foreign troops, significant parts of the country would be captured by the Taliban.

That has not happened, but there is increasing insecurity, with violence shifting to the relatively peaceful north and the Taliban increasing its control of more districts.

The Taliban have also made gains in Helmand in the south-west, and have captured several villages in Kunduz province in recent days.

Also on Tuesday, heavy fighting was reported in the Marawar district of Kunar province in the east.

A BBC reported in Kunar said Taliban fighters were firing mortars into Asadabad, the provincial capital.