Taliban attackers killed six policemen in southern Afghanistan Friday, the government said, as the US military reported ground battles and air strikes left 32 militants dead.

Afghanistan's vast south is the main battlefield between Taliban insurgents opposed to the Western-backed government who are fighting against the Afghan military and about 70,000 international troops under NATO and US command.

Militants attacked a police post in the southern province of Helmand before dawn, killing six policemen, provincial government spokesman Daud Ahmadi said.

Another seven policemen were wounded and in hospital after the battle in the Nawa area outside the provincial capital of Lashkar Gah, Ahmadi said.

A Taliban spokesman, Yousuf Ahmadi, confirmed to reporters that the attack was carried out by his group.

Daud Ahmadi said militants appeared to have struck the police post after a military sweep of three villages in a bid to flush out insurgents overnight.

He said Afghan and foreign troops operating in the same area overnight killed 36 Taliban militants. Officials seized only seven bodies, he said.

The US military released a statement saying its soldiers working with Afghan forces killed 15 militants in the same area Thursday.

It appeared to have been the same incident reported by Daud Ahmadi but this could not be immediately confirmed.

The various forces operating in Afghanistan often give conflicting casualty tolls for the same battles and figures are difficult to confirm independently.

The troops came under attack in the Lashkar Gah area, the US statement said.

"The friendly forces responded with small-arms fire, heavy weapons and close-air support, resulting in the deaths of 15 enemies of Afghanistan," the US military said.

It said a dozen more insurgents were killed in the adjoining Uruzgan province after another attack on an Afghan and coalition patrol.

"The combined force responded with small-arms, rocket-propelled grenade and close-air support fire, killing 12 insurgents," a statement said.

Afghan and coalition forces killed five "combatants" in Kandahar province's Maywand district Thursday, an earlier statement said.

The troops raided a cell "directly linked" to a suicide attack that killed four Afghan civilians and a coalition forces member in January, it said.

The Taliban rose from Kandahar province to sweep into government in Kabul in 1996. They were ousted in a US-led invasion in late 2001 that sent many of their leaders and their Al-Qaeda allies into sanctuaries across in Pakistan.

With extremist violence on the rise in both countries, US President Barack Obama last month unveiled a new anti-terror strategy intended to eliminate the threat from Islamic extremists.

He put Pakistan at the centre of the fight against Al-Qaeda and announced 4,000 more troops to train Afghan forces in addition to an extra 17,000 already committed for the war-torn country.