The Taliban, a hardline Islamist movement that was ousted from government in a U.S.-led invasion in late 2001, claimed responsibility for the attack on the policemen in troubled Kandahar province.
"One of our police posts was attacked in Arghandab district. At this point I can confirm that 11 policemen have been killed," deputy provincial police chief Amanuallah Khan told AFP.
Khan said it appeared that the insurgents were disguised in police uniforms and there were indications that the attack on the walled compound, launched just after midnight, was an inside job.
"Initial investigations indicate that one of the policemen had ties with the Taliban. The Taliban infiltrated the post and opened fire on the police -- there was no exchange of fire," he said.
Police vehicles and weapons were also seized by the attackers, Khan said.
Local witnesses said they heard gunshots for about half an hour after the attack began at the site, which is on a road linking Kandahar to neighbouring Uruzgan province.
A burned-out police pick-up truck and a motorcycle littered the scene while blood was spattered around the room where the policemen were killed, an AFP reporter witnessed.
Interior ministry spokesman Zemarai Bashary confirmed that 11 policemen were killed and another wounded but could not immediately confirm Khan's account of the attack.
Kandahar province is where the Taliban rose to prominence in the early 1990s and is one of the worst hit regions in an insurgency led by the hardline militia since their ouster.
A Taliban spokesman said that rebels had seized 15 weapons and torched two vehicles in the assault on the police post.
"We claim responsibility. Fifty Taliban carried out the attack," spokesman Yousuf Ahmadi told AFP by telephone from an unknown location.
Separately, two NATO soldiers died of injuries sustained in a blast in southern Afghanistan on Sunday, while another two were wounded, the force's spokesman General Carlos Branco said.
The NATO-led International Security Assistance Force did not say where the incident took place or release the nationality of the troops, leaving that to their home countries.
Forty foreign soldiers have now died in Afghanistan this year.
The latest violence comes after the French and Canadian foreign ministers visited Kandahar in the past week to witness the efforts of NATO-led troops to tackle the growing Taliban insurgency and help the country rebuild.
More than 8,000 people, including 1,500 civilians and nearly 220 foreign troops, were slain in the conflict last year, according to a UN report.
Nearly 1,000 Afghan policemen were among the dead. The under-resourced Afghan police force, which lacks the equipment supplied to the US-backed Afghan army, is seen as a weak target by the Taliban.
Meanwhile the U.S.-led coalition in Afghanistan, which operates alongside ISAF, said six militants including a commander "directly" involved in the preparation of suicide attacks in eastern Afghanistan had been arrested.
Mohammad Ghanam and five other militants were captured during a raid by Afghan and U.S.-led troops in the eastern province of Khost, which borders Pakistan, on Friday, the force said in a statement.
Ghanam was part of the Haqqani network, the statement said, referring to a group headed by key Taliban-linked militant leader Jalaluddin Haqqani.