QUETTA Four people were killed and five wounded on Wednesday when a bomb attached to a bicycle exploded in a bazaar in insurgency-hit southwestern Pakistan, police said.

The blast in the remote town of Sibi was the latest in a series to hit the gas-rich province of Baluchistan, where separatist tribal rebels are waging a campaign for greater rights.

'It was a remote controlled bomb fixed to a bicycle in the main bazaar of Sibi. Four people were killed and five wounded, three seriously,' local police officer Mohammad Hussain told AFP.

'Three of the victims were from a pro-government tribe and one was a passer-by,' he said.

'It appears the bombing was a targeted attack. We are investigating if the victims had any rivalry with the bombers,' he said.

Separately one person was injured on Wednesday when a hand grenade exploded at a stall in the provincial capital Quetta which was selling flags for the countrys independence day on August 14, police said.

Another small blast near a road bridge on the outskirts of Quetta on Wednesday caused no casualties, said police.

Impoverished Baluchistan, which borders Iran and Afghanistan, has been hit by years of unrest blamed on ethnic Baluch tribes seeking more political rights and a greater share of profits from the regions natural resources.

Hundreds of people have died in violence in the province since the insurgency flared in late 2004.

The province has also been hit by violence blamed on hardline Taliban rebels, who are not linked to the separatist rebels.