Wardak provincial spokesman Attaullah Khogyani said the attack took place early today next to the police headquarters building in Nirkh district, a Taliban stronghold near Kabul.
Khogyani says the truck bomb was extremely large and destroyed the headquarters. He says another 17 members of the security services were wounded, four critically.
Taliban spokesman Zabihullah Mujahid claimed responsibility for the attack in an email sent to media. Afghan insurgents have increased their attacks in a campaign to retake territory as foreign forces withdraw.
Suicide attacks and roadside bombs are their favoured weapons, but they often result in civilian casualties.