PESHAWAR, Pakistan, Jul 9 (AP) -- Gunmen opened fire inside a factory in the northwestern city of Peshawar on Sunday, killing three Chinese workers, police said.

A fourth Chinese national was seriously wounded in the attack on an auto-rickshaw factory, said Abdul Karim, a senior city police official.

The culprits and the motive for the attack were unknown. Karim said police were examining whether it was an attempted robbery.

He would not speculate on whether militants could be behind the shootings, which occurred in a conservative region near the border with Afghanistan, where Islamic militants are believed to operate.

There have been several attacks blamed on Islamic militants, some of them deadly, on Chinese nationals in Pakistan in recent years.

The abduction by Islamic radicals of several alleged Chinese prostitutes helped trigger the ongoing violent conflict at Islamabad's Red Mosque.

China and Pakistan are neighbors and long-standing allies. Relations between the two countries span close military to economic cooperation.