Afghan civilians on their way to work at a US military base south of Kabul, the capital, have been kidnapped and shot dead, officials have told the AFP news agency.

There was no immediate claim of responsibility, but the Taliban, who the officials blamed for Thursday’s attack, have vowed to increase their attacks during Ramadan.

"Eight Afghan workers who were working in Camp Shank were killed this morning by Taliban," said Rais Khan Sadeq, the deputy police chief in Logar province.

Logar is a stronghold for the Taliban which is waging a 12-year armed battle against the Western-backed government after being toppled in a 2001 US-led invasion.

"They were forced out of their car and taken about 200m off road to a nearby village, and shot in the head one by one," Sadeq told AFP.

Their bodies were found with their eyes blindfolded, the police official said, describing them as "ordinary civilian workers" on the base.

US and NATO military bases across Afghanistan hire local staff to work on construction projects and as cleaners.

Din Mohammad Darvish, the Logar administration spokesman, confirmed the incident and said the bodies of the victims were recovered in the village.

"They were poor and ordinary workers, all civilians," he said.

Deadliest Ramadan attack

It was the deadliest attack since Afghanistan started observing the fasting month of Ramadan, traditionally a time of prayer and charity.

The Taliban have stepped up attacks on Afghan forces since they took responsibility for national security last month.

In the north, police said the Taliban attacked a police post near the city of Kunduz, killing two officers and wounding two others, the only four on duty at the time.

Taliban fighters regularly use roadside bombs to target government officials, and NATO and Afghan soldiers, but civilians and children are also often killed and wounded by the attacks.

According to UN statistics, civilian deaths rose by 24 percent in the first half of 2013 compared to last year.

The UN registered 2,499 civilian casualties between January and June, attributing 74 percent to anti-government forces and nine percent to pro-government forces.

Children accounted for 21 per cent of all civilians killed and wounded, and casualties caused by IEDs - the Taliban's weapon of choice - had risen 41 per cent, it said.

About 100,000 US-led NATO troops in Afghanistan are preparing to withdraw from the country by the end of next year, after key presidential polls scheduled for April.

Source: Agencies