KARACHI: Gunmen on motorbikes on Tuesday opened fire on a police station in Karachi, killing one policeman and wounding two others, officials said.

The attackers fired automatic weapons at the main gates of a police station in the low income and restive eastern suburb of Sohrab Goth and threw an explosive “cracker” which damaged the boundary wall before fleeing, police said.

“At least one policeman embraced martyrdom and two others were wounded after unknown gunmen on motorcycles fired at a police station,” senior police official Aleem Jaffry told AFP.

“The assailants also threw a cracker which damaged the outer wall of the police station,” Jaffry said.

Police spokesman Imran Shaukat confirmed the incident and casualties and added that police had returned fire before the gunmen fled.

The city of 18 million, which is Pakistan's business hub, last year saw its deadliest year in two decades, with around 2,000 people killed in violence linked to ethnic and political tensions.

Pakistan is expected to hold elections by mid-May with the federal parliament due to disband by mid-March. The polls will mark the first democratic transition between two civilian governments in Pakistan's history.