Peshawar: Police say militants armed with assault rifles, grenades and smoke bombs have attacked a police station in northwest Pakistan, killing at least three policemen.

Police officer Sattar Khan says seven other policemen were wounded in Friday's early morning attack in the heart of Peshawar.

Peshawar is close to the border with Pakistan's tribal region, the main sanctuary for Al Qaida and Taliban fighters, and has been a frequent target of the militants.

But this type of attack on a police station in the heart of the city is fairly rare.

A car bomb killed 12 people at an outdoor minibus terminal in Peshawar on Thursday.

Dilawar Khan's son had stopped off at his tea shop on his way back from school when a powerful car bomb exploded outside it. The 12-year-old was among the dozen killed in Thursday's blast at a bus terminal for passengers wanting to travel to the lawless border regions with Afghanistan.

The explosion tore through a dozen vehicles waiting to transport passengers from the city of Peshawar to other areas of the country. Some of the minibuses were blackened and destroyed. There were 32 wounded, including women and children, officials said.

"God should destroy these terrorists," Khan cried at a hospital in the northwestern city of Peshawar.

In the chaos, the 45-year-old shopkeeper initially thought his other son had been killed, but he turned up at home later. "What have my sons done wrong," he said.

Violence has dropped in Peshawar and some other areas of Pakistan over the past year following offensives against the Pakistani Taliban in the north-west. But bombings and shootings still occur often, especially in the border regions, and no one is predicting victory against the militants.

No group claimed responsibility for the blast. Some of the minibuses were blackened and destroyed. The dead included two children, including Khan's son.

Peshawar is located close to the Afghan border, the main sanctuary for Pakistani Taliban fighters at war with the government.

The car bomb was loaded with nearly 45 kilogrammes of explosives, city police chief Siraj Ahmad said.

It's unclear why the bus terminal was targeted. Most militant attacks are aimed at security force or government targets, but markets and other public places have also been hit, presumably to create chaos and add to perceptions the government is unable to provide basic security.