Meanwhile, violent clashes rocked the Libyan city of Zenten southwest of Tripoli on Thursday during which a police post and an office of the local revolutionary committee were torched, Quryna newspaper said on its website.

Separately, lawyers demonstrated in front of a courthouse in Benghazi -- Libya's second city after Tripoli -- to demand a constitution for the country.

The Al-Youm and Al-Manarawebsites, monitored in Nicosia, earlier reported at least four people were killed in the city of Al-Baida, 200 kilometres (120 miles) east of Benghazi, on Wednesday.

Sites monitored in Cyprus and a Libyan human rights group based abroad reported earlier that the anti-Kadhafi protests in Al-Baida had cost as many as 13 lives.

"Internal security forces and militias of the Revolutionary Committees used live ammunition to disperse a peaceful demonstration by the youth of Al-Baida," leaving "at least four dead and several injured," according to Libya Watch.

Al-Bayda is near Benghazi, Libya's second city, where protesters clashed with police and Gaddafi supporters on Tuesday night

New York-based Human Rights Watch said Libyan authorities had detained 14 activists and writers who had been preparing the anti-government protests, while telephone lines to parts of the country were out or order.

Snatches of information were trickling out from parts of the country on an Arabic-language Facebook page used by opposition activists, but the sources were not clear and it was not possible to verify the details.

One post said that protesters in Ar Rajban, near the border with Algeria, set fire to a local government headquarters. In Zenten, south-west of Tripoli, protesters shouted "We will win or die," said another post, which also had a photograph of a building on fire.

In the capital, traffic was moving as normal, banks and shops were open and there was no increased security presence.

Tripoli resident Ahmed Rehibi said anti-government protests were an unnecessary distraction. "We should be concentrating on working, on our schools, because now we are trying to build up our infrastructure," he said.

Analysts say an Egypt-style revolt is unlikely because the government can use oil revenues to smooth over most social problems.

Libya has been tightly controlled for over 40 years by Gaddafi, now Africa's longest-serving leader, and it has immense oil wealth. But the country has nevertheless felt the ripples from the uprisings in neighboring states.

"We have problems," Mustafa Fetouri, a Tripoli-based political analyst and university professor, told Reuters. "This is a society that is still behind in many ways, there are certain legitimate problems that have to be sorted out."

But he said: "I do not really see it (unrest) spreading... Gaddafi remains well respected."

Libya bans all political parties, public dissent is rarely tolerated and over his time in office, rights groups say, thousands of Gaddafi's opponents have been put in prison.

But Gaddafi and his supporters say Libya is a democracy because of his system of direct rule through grass-roots institutions called popular committees.

Opposition activists designated Thursday as a day of protests because it is the anniversary of clashes on Feb. 17, 2006 in Benghazi when security forces killed several protesters who were attacking the city's Italian consulate.

On the eve of the planned protests, SMS messages were sent to mobile phone subscribers saying: "From the youth of Libya to all those who are tempted to touch the four red lines: come and face us in any square or street in Libya."

The four red lines, defined in a 2007 speech by one of Gaddafi's sons, are Islam, security, territorial integrity, and Muammar Gaddafi.