Militants armed with guns and a truck bomb destroyed a police department in Pakistan’s biggest city of Karachi yesterday, killing 18 people and wounding around 100 others, officials said.

One government official said a group of militants first opened fire before detonating a bomb, comparing the explosion to a massive attack that killed 60 people at the five-star Marriott hotel in Islamabad in September 2008.

Pakistan’s Taliban swiftly claimed responsibility for what was a rare attack on government security forces in Karachi, a teeming city of 16 million in the south of the country far removed from militant strongholds in the northwest.

Karachi is Pakistan’s economic capital, home to its stock exchange and the Arabian Sea port where Nato supplies dock to be trucked overland to support the more than 150,000 US-led troops fighting the Taliban in Afghanistan.

Witnesses and police said the building, which belonged to the police’s Crime Investigation Department (CID), collapsed trapping people under the rubble.

An AFP reporter saw dozens of vehicles destroyed and damaged after the attack as rescue workers stretchered casualties into ambulances.

“The building has been completely destroyed. I can see a crater of five metres. Some houses were also badly damaged,” senior police official Tariq Razzaq Dharejo said.

The police chief of Sindh province, of which Karachi is the capital, said 18 people were killed and that the attackers dismantled the security cordon at the department by opening fire on police.