A roadside bomb hit a police vehicle on patrol in southern Afghanistan, leaving five policemen dead and one wounded, a senior police official said on Saturday.

The bomb hit the pickup truck in Trin Kot, the capital of Uruzgan province, late on Friday, senior provincial police officer Gulab Khan told AFP.

"Five policemen were killed and one wounded," he said.

There was no immediate claim of responsibility for the attack, but roadside bombs are frequently planted by Taliban insurgents fighting a decade-long war against NATO-led foreign troops and Afghan government forces.

Afghan police are particular targets for the insurgents, as the country prepares to take over full responsibility for security from some 130,000 foreign troops by 2014.

On Friday afternoon, a car was also hit by a roadside bomb in the Khinjak area of the provincial capital of Uruzgan province, killing one person and wounding two others, according to police spokesman Farid Ail.

Southern Afghanistan remains a key battleground between the insurgents and foreign forces despite a surge of US troops in 2010 and 2011.

Around 80 percent of the 3,000 Afghan civilians killed in 2011 were victims of attacks by the Taliban, who were toppled in late 2001 by a US-led invasion, according to a UN report released last week.

The Taliban announced last month that they planned to set up a political office in Qatar, widely seen as a move towards peace negotiations with Washington and its Western allies.