TRIPOLI (Reuters) – At least 20 protesters were killed overnight in the Libyan city of Benghazi, a rights watchdog said on Sunday, after witnesses said security forces fired heavy weapons at civilians from a fortified compound.

The New York-based Human Rights Watch said the latest night of violence took the death toll from four days of clashes centered on Benghazi and surrounding towns beyond 100.

The unrest, the worst in Libyan leader Muammar Gaddafi’s four decades in power, started as a series of protests inspired by popular revolts in neighboring Egypt and Tunisia, but was met by a fierce response.

A picture pieced together from witness accounts suggested that the city is in a cycle of violence, where people are killed and then, after funeral processions to bury the dead the next day, security forces shoot more protesters.

Conflicting accounts were given over poor phone lines but it appeared the streets were under the control of protesters while security forces had pulled back to a high-walled compound, known as the Command Center, from where they shot at people.

“A massacre took place here last night,” one Benghazi resident, who did not want to be named, told Reuters by telephone on Sunday.

He said security forces were using heavy weapons, adding: “Many soldiers and policemen have joined the protesters.”

A Benghazi hospital doctor said victims had suffered severe wounds from high-velocity rifles.

“CIVIL MUTINY”

Another witness, a leading tribal figure who requested anonymity, suggested the security forces remained confined to their control center.

“The state’s official presence is absent in the city and the security forces are in their barracks and the city is in a state of civil mutiny,” he told Reuters. “People are running their own affairs.”

He said that, as on previous days, thousands of people were gathered near the northern Benghazi courthouse. He said they were chanting: “We want to bring down the regime … Allahu Akbar!”

Human Rights Watch said at least 20 more people had been killed in Benghazi on Saturday, taking the overall toll, compiled from interviews with witnesses and hospital officials, to a “conservative” 104.

The Libyan government has not released any casualty figures or made any official comment on the violence.

Libyan analysts say it is unlikely for the moment that Gaddafi will be overthrown because the unrest is largely confined to the eastern Cyrenaica region where his support has traditionally been weaker than in the capital Tripoli, 1,000 km (600 miles) to the west, and the rest of the country.

The crackdown prompted about 50 Libyan Muslim religious leaders to issue an appeal, sent to Reuters, for the security forces, as Muslims, to stop the killing.

“We appeal to every Muslim, within the regime or assisting it in any way, to recognize that the killing of innocent human beings is forbidden by our Creator and by His beloved Prophet of Compassion (peace be upon him) … Do NOT kill your brothers and sisters. STOP the massacre NOW!” the appeal said.

Foreign reaction to the unrest in Libya, a major energy producer with significant foreign investment, has so far been muted, but Britain called for a stronger response.

“The world should not hesitate to condemn those actions,” Hague told Sky News. “What Colonel Gaddafi should be doing is respecting basic human rights, and there is no sign of that in the dreadful response, the horrifying response, of the Libyan authorities to these protests.”

TEXT APPEAL

Some analysts have said there may be negotiations between Gaddafi and eastern tribal leaders, and an SMS message sent late on Saturday to Libyan mobile phone subscribers hinted at a more conciliatory approach.

“All citizens and youth of Benghazi, those who died among the civilians and police are all sons of our country. Enough of what has happened and stop the bloodshed.”

In Tripoli, several thousand Gaddafi supporters rallied in the city’s Green Square until the early hours of Sunday morning, a Reuters reporter said.

They chanted “God, Libya and Muammar!” and “Muammar is the pioneer of Arab nationalism!”.

Libya’s state news agency said some cities had seen acts of arson and vandalism, and blamed “a foreign network trained in creating clashes and chaos so as to destabilize Libya”.

Sir Richard Dalton, a former British ambassador to Libya, told the Independent on Sunday newspaper that Gaddafi would find it hard to make concessions in order to survive.

“I think the attitude of the Libyan regime is that it’s all or nothing,” he said.

Witness accounts have been hard to verify independently because Libyan authorities have not allowed foreign journalists into the country since the protests erupted and local reporters have been barred from traveling to Benghazi.

Mobile phone connections have often been out of service and Internet service in Libya has been cut off, according to a U.S. company that monitors web traffic. People in Tripoli said they had Internet access late on Saturday.