The fighting started Thursday night in the village of Kumbarak in Helmand province, and Nato forces told residents to evacuate their homes because of the clashes, said Gereshk district chief Abdul Manaf Khan.

The airstrikes killed 50 Taliban and up to 40 civilians, Khan said, citing villagers' reports. He said the bodies have already been buried, and the fighting continued Friday.

Afghan authorities and foreign forces said Friday they were checking claims that up to 40 civilians were killed in an overnight air strike by international troops.

The alleged incident happened in southern Helmand province, a hot-bed of Taliban insurgents where US-led forces say scores of militants have been killed in recent days.

"Foreign troops destroyed five civilian houses in a four-hour aerial bombardment last night, killing 40 civilians," Mualim Mirwali, an MP for the province, told AFP.

The MP said rescuers brought out 40 bodies from the rubble in the province's Bawri village but more were feared buried underneath.

The provincial police chief, Mohammad Hussain Andiwal, said he had heard the reports but could not confirm civilian casualties.

But Abdul Manaf, the governor of a neighbouring district, said he was told 28 people had been killed after foreign troops warned Afghan civilians to flee the village because of possible operations.

"People were told to leave the area, but last night as people were still leaving, foreign forces bombed the area killing 28 civilians and eight others were wounded," he said.

Manaf said around 50 Taliban were also killed in the area on Wednesday.

Nato's International Security Assistance Force said it did not have any information about the incident and was looking into it.

The report could not be immediately verified due to the area's remoteness and instability, although a local lawmaker and a resident also said there were civilians among the dead.

Malim Mirwali, a member of Parliament for Gereshk, said that more than 40 civilians were killed in the airstrikes a figure that one local resident also cited.

"The war planes came and bombed these villagers more than 40 civilians killed, including women and children," said villager Nimatullah Khan.

"The villagers' bodies were buried this morning because the weather was hot. Right now, the people are scared, and the operation is ongoing between these forces and the Taliban," he said.

The latest violence comes a day after reports of US-led coalition and Afghan troops battling with militants in the south, leaving more than 60 suspected Taliban dead. A Nato soldier was killed in another incident.

Violence has risen sharply in Afghanistan in the last two months. More than 3,500 people, mostly militants, have been killed in insurgency-related violence this year, according to an Associated Press tally of casualty figures provided by Western and Afghan officials.

Civilian deaths are a recurring problem that Afghan President Hamid Karzai has repeatedly deplored, demanding foreign forces take greater care to avoid such incidents.