Four Afghan policemen were killed on Friday as the Taliban have stepped up their attacks against government and NATO troops to undermine the U.S.-led coalition's effort to build up Afghan forces.

The policemen died in three separate incidents in Helmand province in southern Afghanistan, according to police officials AP reported.

One was killed when the Taliban attacked in Marjah district. A second died when a roadside bomb he was searching for exploded in Washer district. Two others were killed when their vehicle struck a roadside mine in Gereskh district.

In neighboring Kandahar province, a fuel tanker overturned and caught fire on Friday, killing seven people, police said.

Kandahar provincial police chief Gen. Abdul Razaq said three other civilians were seriously wounded in the morning incident in Panjwai district.

The Taliban claimed they fired a rocket at the fuel tanker, causing it to explode. But Razaq said no rockets were fired.

He said the tanker caught on fire after it overturned and that a passing car was also set ablaze.