Afghan police clashed with Taliban fighters outside the capital Kabul, leaving a dozen militants and an officer dead, while four more policemen were killed in a bomb blast, the government said.

The militants were killed in a sweep to clear Taliban from Musayi district about 15 kilometres south of Kabul on Monday, interior ministry spokesman Zemarai Bashary told AFP.

"The head of the district criminal investigation department was wounded and later died in hospital. Twelve enemies were also killed," Bashary said.

The fresh violence was linked to a deadly insurgency led by the extremist Taliban, who are battling to wrest back power after being ousted from government by the 2001 US-led invasion.

Also Monday, a roadside bomb blew up a police vehicle in the eastern province of Paktia and killed four policemen, the ministry said.

The vehicle was struck while taking part in an operation with the army and US-led troops in Zurmat district, it said in a statement.

The Taliban-led insurgency has steadily gained strength in recent years, with 2008 the deadliest of the campaign.

There are about 70 000 US-led and NATO-led troops deployed in Afghanistan to help the fragile nation fight extremism, which the West brands a direct threat.

British Prime Minister Gordon Brown visited Kabul on Monday to drum up support for a new strategy to tackle a "crucible of terrorism" on the Pakistan-Afghan border.