The three attackers first opened fire with Kalashnikovs, then used hand grenades to blow their way into the building before detonating their suicide vests, senior police official Yameen Khan told AFP.
He said the station was targeted because it housed a large number of officers in downtown Peshawar, which runs into Pakistan's lawless tribal belt, a hotbed of Taliban and Al-Qaeda-linked militants targeted by US drone strikes.
Pieces of human flesh and body parts, including the head of one of the suicide bombers, were scattered inside the police station, along with broken windows and chairs, an AFP reporter said.
"Four policemen have been killed and four others were wounded," Khan said.
"The attackers wanted to kill the maximum number of policemen, that is why they selected this station. Around 200 policemen reside here," Khan told AFP.
The attack came a day after a car bomb ripped through a bus station on the outskirts of Peshawar, killing 13 people, including two children, raising concerns about a new wave of violence in the city of 2.5 million.
More than 530 bomb attacks have killed around 4,900 people across Pakistan since government troops in July 2007 stormed a mosque in Islamabad where Islamist extremists were holed up, provoking a local Taliban-led insurgency.
But there was a decline in attacks in the second half of 2011, with at least some commanders in Pakistan's nebulous Taliban movement abiding by a ceasefire.
The bombers struck at around 7:15 am when local residents in the congested Kotwali area were leaving home for work and school.
"The attackers first started firing on the gate of the police station and then used the hand grenades. Later they entered inside the police station," Imtiaz Khan, a senior police official, told AFP.
Witnesses said the attack happened as policemen came off the night shift.
"We were just trying to sleep after we finished night duty when we heard the blast," said police constable Sayed Ali, who lives at the station.
"We ran out of the building from the back door and then there were three blasts," he told AFP.
Officials said 15 to 18 kilograms (33 to 42 pounds) of high quality explosives were stuffed into the suicide vests, along with steel plates and ball bearings.
Shafqat Malik, chief of the bomb disposal squad in Peshawar, said that the suicide bombers were aged between 18 and 22.