Muammar Gaddafi vowed to "crush any enemy" on Friday, addressing a crowd of supporters in Tripoli as Libya's popular uprising closed in around him.

"We will fight if they want," the 68-year-old leader declared after a day of clashes all over the capital between security forces and crowds of protesters, which Gaddafi's opponents said had left some districts in their hands.

With eastern Libya already under opposition control after a week of unrest, protesters held the centre of Zawiyah, west of the capital, a witness said, and laid makeshift defences to fend off government forces after successive fierce attacks.

A string of other towns were reported to have fallen to the opposition, but Gaddafi retained the defiance he has often displayed against the West over more than four decades in power.

"Get ready to fight for Libya, get ready to fight for dignity, get ready to fight for petroleum!" he urged the crowd of thousands in Tripoli's central Green Square, threatening to open military arsenals to his supporters and tribesmen.

"We can crush any enemy. We can crush it with the people's will," he said, shouting and waving his fists.

U.N. High Commissioner for Human Rights Navi Pillay said "thousands" may have been killed or injured by Gaddafi's forces in the uprising, and called for international intervention to protect civilians.

Prosecutor-general Abdul-Rahman al-Abbar became the latest senior official to resign, and told al Arabiya he was joining the opposition. Libya's delegations to the Arab League and the United Nations in Geneva also switched sides.

In the first practical attempt to enrol the support of Libya's 6 million citizens since the uprising began, state television announced the government was raising wages and food subsidies and ordering special allowances for all families.

Gaddafi's four decades of totalitarian rule have stifled any organised opposition or rival political structures, but in the east, ad hoc committees of lawyers, doctors, tribal elders and soldiers appeared to be filling the vacuum left by Gaddafi's government with some success.

Reuters