Gunmen ambushed a police checkpoint on Monday in Pakistan's troubled northwestern city of Peshawar, killing two policemen, an official said.

Three gunmen riding two motorbikes attacked the police checkpoint on the outskirts of Peshawar and escaped after the attack.

"We don't know about the identity of the attackers but the militants fled towards the tribal region after killing two policemen at the checkpoint in Pashta Khara area," Imran Shahid, a senior police official, told AFP.

The attack came a day after Islamic militants killed at least 53 people in suicide and bomb attacks in the country's northwest and southwest.

A car bomb targeted a security forces' convoy and killed 17 people in the suburbs of Peshawar on Sunday, not far from the semi-autonomous tribal belt where Taliban and Al-Qaeda-linked groups have bases.

Also on Sunday a suicide bomber blew himself up close to a mosque in the southwestern city of Quetta, killing at least 28 people, to mark the deadliest day in months.

Pakistani troops have been fighting for years against homegrown insurgents in the tribal belt, which Washington considers the main hub of Taliban and Al-Qaeda militants plotting attacks on the West and in Afghanistan.