Four officers were killed when suicide bombers armed with assault rifles and grenades attacked a large police station in Pakistan's north-western city of Peshawar.
City police chief Imtiaz Altaf said three militants entered the compound after attacking the main gate, then blew themselves up when police returned fire.
"They wanted to occupy this police station, but they failed," he told reporters.
Four policemen were killed and six injured in the attack, said police officer Sattar Khan.
There were more than 370 police officers in the station at the time of the assault, said provincial information minister Iftikhar Hussain.
He blamed the attack on the Pakistani Taliban - a group that has waged a bloody insurgency against the Pakistani government - and speculated that the attackers wanted to take the police hostage.
The number of officers was so high because authorities send graduates of the police training academy to the station for 18 months before allocating them to other posts.
Authorities said the attack was probably in revenge for offensives against nearby strongholds.
The attack was the latest in a surge of violence in or close to Peshawar, showing that local militants retain the capacity to strike. The army has claimed success in its fight against militants behind five years of violence in the country, but the insurgents have proved resilient.
Peshawar has been a frequent target of militant attacks over the last few years, but most have been bomb blasts, not co-ordinated assaults in the centre of the city such as the latest attack.