Najib Danish, deputy spokesman for the Interior Ministry, says a suicide car bomber first detonated his vehicle at the entrance and opened the way for other attackers to enter the compound.
He says two of the attackers were shot by security forces and probably one more attacker is still resisting.
He says three policemen have been wounded in the attack, which took place today in Gardez, the provincial capital.
Taliban spokesman Zabihullah Mujahid has claimed responsibility for the attack in a statement sent to the media. Mujahid says fighters are inside the police compound battling police.