Protesters blocked key highways in a volatile southwestern province Wednesday in unrest sparked by the killing of a top tribal chief in a Pakistani army raid at the weekend, officials said.

Police also announced that up to 700 people have been detained since riots erupted Saturday after Nawab Akbar Bugti, a fugitive political and militia leader, was killed in his mountain hide-out.

Baluchistan police chief Chaudhry Mohammed Yaqoob said scores of protesters have blocked two roads linking the Baluchistan provincial capital of Quetta to the southern port city of Karachi and one heading west to Iran.

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Another key road linking Gawadar, a remote Baluchistan town on the Arabian Sea coast, with Karachi, was also blocked by boulders and crudely erected barricades, Yaqoob said.

Bugti supporter Habib Jalib said angry Baluch tribesmen were blocking all roads into Baluchistan in their continuing protest over the death of the tribal chief, who led an often violent campaign against government forces for greater control of natural resources extracted in this region.

"More than 70,000 of our supporters are active across Baluchistan to record their protest against the killing of their beloved leader," said Jalib, a senior figure in the Baluch Solidarity movement, an alliance of four ethnic-Baluch political groups that ordered the highways blocked.

Police are in contact with Bugti supporters to try to open the roads, officials said.

Police chief Yaqoob said between 650 and 700 people have been arrested during four days of violence that has seen scores of government buildings, businesses and vehicles burned. Jalib said police have arrested 850 alliance supporters throughout Baluchistan since Saturday. The difference in the numbers could not be immediately reconciled.

At least six people have been killed, including two during fiery protests and four in a Tuesday bombing at a roadside restaurant. It was unclear if the blast was linked to the Bugti protests.

There were no immediate reports of violence in Quetta on Wednesday, unlike a day earlier when angry protesters threw hand grenades at police and set fire to 20 businesses following a funeral service held for Bugti in a stadium attended by at least 10,000 people.

The highway blockade forced most shops in Quetta to close Wednesday, while dozens of buses were parked at a terminal in Quetta unable to leave for Karachi and the eastern city of Lahore, according to an Associated Press Television News cameraman at the scene.

On Tuesday, the military said it had not yet retrieved Bugti's body from the cave that collapsed on him and several of his supporters in an unexplained explosion. It was unclear when, or if, soldiers would be able to sift through piles of rubble in the cave at Kohlu, 220 kilometers (140 miles) east of Quetta, where Bugti had been holed up in since December.

Two Bugti supporters in Quetta demanded authorities recover his body for a proper burial.

"We are ready to give him a proper burial if they give us the body. If they don't, we cannot do anything," said Nek Mohammed, 38. "This is an extreme atrocity that has happened to us."

Bashir Ahmed, aged in his 20s, said: "This problem will be solved if his body is found.