Around 5,000 Chinese people live and work in Pakistan where they are engaged in several Beijing-funded development and engineering projects, many of which are opposed by various insurgent groups.

A suicide attack aimed at Chinese workers in southwestern Baluchistan province on Thursday, which killed at least 29 Pakistanis, was the deadliest in a series of such incidents.

"It is a vital relation for Pakistan but it appears that somebody wants to damage it," foreign office spokeswoman Tasnim Aslam told AFP after the blast in the industrial town of Hub.

China told Pakistan earlier this month to step up security for its citizens after three Chinese workers were shot dead in Peshawar in retaliation for a deadly government operation against a radical mosque in Islamabad.

The crackdown against the pro-Taliban Red Mosque was itself sparked by the kidnappings of seven Chinese people from an acupuncture clinic in the capital by Islamist students who accused them of prostitution.

It was unclear who was behind Thursday's attack but police said they were investigating whether it was linked to a wave of other blasts and ambushes across the country following the mosque carnage.

Earlier attacks on Chinese nationals in Baluchistan have been claimed by separatist, non-Islamic tribal rebels fighting for greater autonomy and a share of profits from the proceeds of the province's natural gas reserves.

A May 2004 car bomb blamed on the insurgents killed three Chinese engineers developing a Beijing-funded deep sea port at Gwadar on the Arabian Sea. In February 2006 three more Chinese engineers were shot dead in the same region.