KABUL: The Taliban took control of a large police base in remote northeast Afghanistan after some 100 police and border officers joined the insurgents following three days of fighting, security officials said Sunday, the largest mass surrender since US and Nato forces ended their combat mission.

The loss of the Tirgaran base in once-peaceful Badakhshan province shows the challenge facing Afghan forces, in charge of the country's security since the start of this year.

Remote bases and checkpoints increasingly find themselves targeted by the Taliban and other fighters as casualty rates for Afghan police and soldiers soar.

The police base, in the province's Wardoj district, had been cut off as heavy rains destroyed roads into the area, said Gen Baba Jan, Badakhshan province's police chief.

It wasn't clear why soldiers hadn't been flown into the area to support the base, though the province's steep valleys often make aircraft landings difficult.

“No reinforcements were sent to help the police at the base for the past three days when they were under the attack and finally they had no option: They had to join the Taliban,” said Abdullah Naji Nazari, the head of Badakhshan's provincial council.

Jan said the local police commander also joined the Taliban and handed over the base's extensive weapons and ammunition cache.

The Taliban issued a statement saying they captured the base along with 110 police officers, their local commander and the head of the local border police. It did not say whether the captives joined their ranks.

The loss of the base comes after an attack last month saw hundreds of insurgents assault security checkpoints in the province's Yamgan district, forcing police to abandon them.