The number of civilian dead in May was the highest in months, spokesman Adrian Edwards told reporters.

Last month those killed by national and foreign forces supporting the government appeared to "largely exceed" those killed by rebels, Edwards said, without providing figures.

However for the whole year, information from various sources indicated that "there are about 600 deaths by anti-government and pro-government forces up till now," Edwards told AFP later.

About 52 percent were by pro-government forces and 48 percent by anti-government forces, he said.

Some of this information was based on figures verified by the UN, but in areas where its staff was not able to travel it came from second-hand sources, he said.

"It's important to emphasise that our database is not an absolute measure of civilian casualties," Edwards said.

The foreign forces in Afghanistan have come under fire for civilian casualties in operations against Taliban.

In the most recent case, elders said 45 civilians, including women and children, were killed in air strikes by the Nato force and US-led coalition in the southern province of Helmand late Friday.

If confirmed, this would be the highest number of civilians killed in foreign military action since 2002, a year after the Taliban were removed from power in an operation led by the United States.

Sixty-two Taliban were also killed in the strikes in Helmand's Girishk district, the elders said.

President Hamid Karzai has sent a team to the remote area to investigate.

Just over a week ago he berated the foreign forces for killing civilians by using extreme force and not coordinating their operations with their Afghan counterparts.