Pakistan put its paramilitary forces on "red alert" across the country on Thursday after the assassination of opposition leader Benazir Bhutto sparked violent protests by her supporters.

President Pervez Musharraf denounced what he called a terrorist attack and appealed for calm after angry backers of the slain former prime minister took to the streets across Pakistan, from the Himalayas to the southern coast.

The unrest was predictably fiercest in her native Sindh province and its capital, Karachi.