A man set off a bomb in a department store in China's northwest, killing himself and a police officer who was trying to stop him, a police official said Friday.

Two officers were injured in the bombing at the Tianshan Department Store in Urumqi, capital of the Xinjiang region, according to the official of the Urumqi police. He would give only his surname, Shi.

Shi said the bomber's identity was still under investigation. But the official Xinhua News Agency identified him as a migrant worker who it said was angry over a pay dispute.

Bombs are often used in attacks linked to business or personal disputes in China, where guns are rare but explosives are easy to obtain.

Xinjiang has witnessed a series of bombings blamed on guerrillas fighting to end Chinese rule in the predominantly Muslim territory.

There was no indication that the blast Friday was linked to separatists.