NICOSIA (AFP) – Six people were killed in the Libyan city of Benghazi on Thursday, as Moamer Kadhafi's regime sought to overshadow an opposition "Day of Anger" with its own rally in the capital Tripoli.

Meanwhile, clashes broke out in the city of Zentan, southwest of the capital, in which a number of government buildings were torched.

Violent clashes in the Mediterranean coastal city of Benghazi have so far left six dead on Thursday, the Al-Youm and Al-Manara sites reported on what was the third straight day of protests against the long-time Libyan leader.

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

The websites, monitored in Nicosia, said 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.

Geneva-based Human Rights Solidarity, citing witnesses, said rooftop snipers in Al-Baida -- a city of 210,000 inhabitants -- had killed 13 protesters and wounded dozens of others.

But the Quryna newspaper, close to Kadhafi's son Seif al-Islam, cited official sources and put the death toll at two. It traced the unrest to a police shutdown of local shops that soon escalated.

The interior ministry fired the head of security in Al-Jabal Al-Akhdar province in the aftermath of the violence, in which protesters had torched "several police cars and citizens," the paper said on its website.

Videos circulating on the Internet showed dozens of young Libyans apparently gathered on Wednesday night in Al-Baida chanting, "The people want to bring down the regime," and a building which had been set on fire.

In Tripoli, the situation was calm early on Thursday. A pro-regime rally was organised in Green Square, near the capital's water front, with students being bused in to take part.

Traffic was lighter than usual and the security presence on main roads slightly boosted, after text messages went out on Libya's mobile telephone network on Wednesday warning against street protests.

The messages, circulated from "the youth of Libya," warned against crossing "four red lines: Moamer Kadhafi, territorial integrity, Islam and internal security."

"We will confront anyone in any square or avenue of our beloved country," the messages read.

The Revolutionary Committees, the backbone of Kadhafi's regime, have warned they would not allow anti-regime protesters to "plunder the achievements of the people and threaten the safety of citizens and the country's stability."

And in Zentan, southwest of the capital, Quryna said clashes had broken out and that demonstrators had set fire to the police station, the city's court, the posts of the internal security forces and the people's guard, and the local offices of the Revolutionary Committees.

It said no one had been killed, but did not say whether anyone had been injured. It also said several demonstrators had been arrested.

The response to Thursday's protest calls was being seen as a test for Kadhafi, 68, who has been in power since 1969. His counterparts in neighbouring Egypt and Tunisia have been toppled in uprisings over the past month.

One Facebook group urging the Day of Anger for Thursday had more than 22,000 followers.

On Wednesday night, Kadhafi was seen on television being mobbed by thousands of supporters as he laid the foundation stone of a sports complex for popular football club Ahly Tripoli.

Britain, France and the European Union called for restraint by the authorities in Libya, whose relations with the West have improved sharply over the past decade after years of virtual pariah status.

Britain underlined "the right of peaceful assembly," France deplored the "excessive use of force" and reaffirmed its "attachment to ... the right to demonstrate peacefully everywhere in the world" and the European Union urged Libya to allow "free expression."

The United States said it encouraged Libya, like countries throughout the Middle East and North Africa, to take steps to meet the hopes and needs of their people.

The Day of Anger was called to mark the deaths of 14 protesters in an Islamist rally in Benghazi in 2006.