Rioting has broken out in southwestern Pakistan after police said they found the bodies of three missing political dissidents.

Police say one officer has been shot dead in southwestern Pakistan during the rioting.

Ghulam Ali Lashari, a senior police official, said the officer was fatally wounded when protesters opened fire in Khuzdar, a town in Pakistan's restive Baluchistan province.

Television footage showed police swinging batons to disperse protesters who set fire to a bus in the city of Quetta, the capital of Baluchistan province.

Police official Khalid Masood says the mutilated bodies of three ethnic Baluch nationalist leaders were found before dawn on Thursday in another part of the province.

Some Baluch groups have waged a long, low-level insurgency against the central government demanding more autonomy or secession for the impoverished but resource-rich province.