Suspected Taliban fighters have detonated suicide bombs and then stormed a bank branch in the southern Afghan province of Helmand, officials have said, adding a total of 13 people died in the incident.

A spokesman for the Helmand governor said that the fighters engaged in a firefight with security forces on Wednesday, adding that six attackers, four security guards and three civilians have been killed in the incident. He also said an unknown number of civilians were inside the three-storey building and firefight was still going on. 

Blasts and gunfire were heard at the scene of the attack targeting the Kabul Bank branch in the city of Lashkar Gah.

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"At least two large explosions have gone off before the firefight started," Al Jazeera's Jennifer Glasse, reporting from Kabul, said.

"Officials said that it is towards the end of the month and police officers in large numbers have been going to that bank to get their salaries. Officials added that this might be the reason the bank was targeted," she added.

"According to our information, there were four Taliban [fighters], one of them detonated his explosives and three are fighting with security forces," Farid Ahmad Obaid, the spokesman for Helmand's police chief, was quoted as saying by Reuters news agency.

"In a separate incident in the eastern city of Jalalabad, a bomb attack killed two policemen and wounded five," Al Jazeera's Glasse said.

"These are the last days of the NATO combat mission in Afghanistan, which makes people worry about the deteriorating security situation in the country."

On December 31, the US-led NATO combat mission in Afghanistan will end after 13 years of fighting the Taliban.

It will be replaced by a 12,500-strong support mission to advise and assist the Afghan security forces.

Source: Al Jazeera and agencies