"Taliban attacked under the cover of darkness during the night, but our security forces fought against them well and prevented any damage to the camp," General Ghulam Farooq Parwani, deputy commander of Maiwand 215 military corps said on Friday.

Camp Bastion was handed over to the Afghan military as part of the coalition's withdrawal of most foreign troops by the end of 2014.

General Parwani said five of his men had been killed, along with 20 Taliban fighters, and the battle was continuing. The figures could not be verified.

The Taliban, who were ousted from power by the U.S.-led coalition in 2001, claimed that hundreds had been killed in the attack. The insurgents routinely inflate casualty figures in statements.

On Wednesday, a coalition air strike killed six Taliban militants preparing to launch attacks on army personnel, according to the Helmand governor's spokesman. The coalition declined to comment.

More than 4,600 Afghan police and soldiers have been killed in the war against the Taliban since the start of the year.

Elsewhere in Afghanistan, 20 people were wounded by a bomb planted in a mosque in eastern Nangarhar province, an interior ministry official said, while three people were injured in an explosion in northern Balkh province.