The blasts were apparently timed so emergency personnel who rushed to the scene of the first blast would be struck down by the second, police sources told China's official Xinhua News Agency.
The first explosion occurred at a construction site in the town of Shora and caused no casualties. It was followed up by a second bomb that killed a policeman and two soldiers and wounded another 30 people, including several police officers and soldiers along with four children.
Xinhua said Shora is in an area that has been a hotbed of insurgent activity for years.
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