An apparent bomb explosion in southeastern Pakistan has killed three Chinese nationals and left 11 others injured, some critically. The explosion occurred Monday morning as a group of Chinese engineers rode by bus to a seaport development site in Balochistan Province.

The victims include a Pakistani driver and security guard.

The provincial police chief, Shoaib Suddle, says the incident is under investigation. "They were just about to cross [by] another auto-car which was parked on the roadside, and at that moment an explosion took place," he says. "We are still trying to find out the cause of that explosion."

A local police official described the explosion as a bomb attack and said it was likely caused by a remote-control device.

The Chinese engineers were one of several international teams working on a project to improve port facilities at the coastal city of Gawadar, on the Arabian Sea.

Pakistan hopes the development plan will ease traffic at Pakistan's main shipping hub of Karachi.

Some of those injured in the explosion were airlifted to Karachi for medical treatment.

The incident follows a terror attack in Balochistan in March, in which gunmen fired on a religious procession in the provincial capital, Quetta, killing more than 50 people.