At least 20 people have been injured in a bomb blast at a pro-autonomy rally in Pakistan's Baluchistan province, police say.

Nazir Ahmad, a police official, said a bomb rigged to a parked motorcycle had detonated on Tuesday near the rally's stage in the town of Jaaferabad, leaving some people in a critical condition.

The Reuters news agency reported that there were a number of bodies at the scene of the blast.

The rally was held to mark the second anniversary of the killing during a military operation of Nawab Akbar Bugti, a tribal chieftain and former Baluchistan governor.

Bugti led an armed campaign to pressure the central government to award Baluchistan a larger share of money from oil and gas extracted from the region.

Supporters continue to demand political autonomy for the vast, gas-rich province.

Hundreds of people have died in the province since fighting flared in late 2004. The province has also been hit by attacks blamed on Taliban supporters.

Diplomat attacked

In an unrelated incident, armed men opened fire on the car of a US diplomat in Peshawar, capital of Pakistan's North West Frontier province.

Police and US officials said Lynne Tracy, the principle officer for the US consulate in Peshawar, escaped the attack without injury on Tuesday.

Lou Fintor, spokesman for the US embassy, said: "There were no injuries and minimal damage to the vehicle. We are co-ordinating with Pakistani authorities in investigating the incident."