The attack, claimed by the Taliban, began around 6:30am (local time) when one bomber detonated a car packed with explosives at the gate of the police headquarters in Gardez city, capital of Paktia province, said Najib Danish, a spokesman for the Interior Ministry.
Four more attackers stormed the gate after the blast, with at least two quickly killed by police. The others held out against Afghan special forces that had responded to the attack, he said.
Danish put the toll at two police killed and five wounded.
However, doctors at the city hospital said they had received the bodies of at least five police, as well as at least 30 wounded people, including 20 civilians.
The Taliban claimed responsibility for the attack, with spokesman Zabihullah Mujahid reporting more than 100 police were killed and wounded.
The Islamist group often exaggerates casualty numbers in attacks against government targets and security forces.
Photo: AFP Afghan policemen at the site of the suicide bombing attack.