LASKAR GAH: Afghan police were holding out against Taliban forces who have surrounded their compound in Sangin, in the southern province of Helmand, on Monday as the militants closed in on another district capital.

"Right now there is a heavy fight going on between Afghan security forces and Taliban in Sangin in the district governor's building and the police chief's headquarters," Helmand governor, Mirza Khan Rahimi, told Reuters.

He said Taliban fighters were outside the compound walls and the situation risked slipping entirely out of control.

In Kabul, Abdullah Abdullah, chief executive of the National Unity Government with President Ashraf Ghani, pledged "immediate action" after a meeting with security ministers.

"This action will repel enemy attacks," he said.

However, any action may come too late to save Sangin, where one police official, who spoke on condition of anonymity, said there was no question of holding on to the district and it was now a matter of trying to save the lives of about 170 police holding out.

"If we don't get urgent assistance from the local government, we will lose all our forces," he said.

He said roads into Sangin were completely controlled by the Taliban and unless army units broke through it would not be possible to relieve the police.

The situation in Helmand carries sharp echoes of the situation that led to the Taliban's biggest success in the 14-year war, their brief capture of the northern city of Kunduz in September.

Helmand, a major centre of opium cultivation and a traditional Taliban heartland that British and American forces struggled for years to control, has been the scene of fierce fighting for months.

Army and police units have complained of being left without adequate supplies and reinforcements as the Taliban seized three districts and threatened other centres including the provincial capital, Laskar Gah.

On Sunday, Helmand Deputy Governor Mohammad Jan Rasulyar issued an unusual open plea to Ghani on Facebook, warning that Sangin was "on the verge of collapse" and the whole province could follow.

Reports of mass desertions, poorly performing and badly supplied army units and weak leadership have underlined the problems facing government forces fighting alone since the withdrawal of international troops from combat last year.

The fighting comes as Afghan and Pakistani officials have been pushing for a resumption of peace talks with the Taliban, broken off after the announcement in July that the movement's leader, Mullah Mohammad Omar, had died two years earlier.

That announcement triggered a bloody leadership struggle within the Taliban. But divisions have done nothing to lessen the effectiveness of fighters who have conducted a series high-profile attacks over recent months.