The Taliban claimed responsibility for the attack which took placenear the border with Pakistan.

A car bomb exploded in the Afghan troubled province of Kandahar, killing three policemen on Monday, police said.

"A car bomber approached the national police patrol cars and smashed his car into the police vehicles, killing three policemen and destroying the vehicle," General Abdul Raziq, chief of Kandahar's border police, told AFP news agency.

The Taliban claimed responsibility for the attack which took place in Spin Boldak district in southern Afghanistan, near the border with Pakistan.

The attack comes three days after a Taliban suicide bomber killed a police commander and 16 others at a public bath in the same district, in the attack in Afghanistan since October.

 US Defense Secretary Robert Gates last week ordered an extra 1,400 US Marines to the south in a bid to anticipate a traditional spring offensive by Taliban, which is expected in April or May.