Libya was approaching a "tipping point" last night as widespread protests against Colonel Gaddafi's regime were met with increasing violence from security forces.

Dozens of protesters were reported killed by sniper fire from security forces in Benghazi, Libya's second city, yesterday when violence flared again as crowds clashed after funerals for people killed in fighting on Friday. "Dozens were killed. We are in the midst of a massacre here," one eyewitness reported.

Clashes were reported in the town of al-Bayda, where dozens of civilians were said to have been killed and police stations came under attack. In all, the death toll was reported to have reached 120. Doctors from Aj Jala hospital in Benghazi confirmed 1,000 people had been injured.

The widespread violence on Friday culminated in at least 35 deaths, according to Human Rights Watch. The New York-based watchdog said its tally was now 84 after three days of violence. The Benghazi-based Quryna newspaper, reportedly linked to one of Colonel Gaddafi's sons, said 24 were killed. Other reports put the body count higher, with as many as 200 dead and more than 1,000 hurt.

Experts warned the Gaddafi regime was unlikely to make the sort of compromises seen recently in other Arab countries. Sir Richard Dalton, former British ambassador to Libya, said: "Gaddafi will 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."

The disturbances in Libya differ markedly from those in Egypt, Tunisia and other parts of the Middle East, in that protesters opposed to the current regime are clashing directly and violently with Gaddafi supporters.

Libya-watchers are now waiting anxiously to see if protests spread to the capital, Tripoli. Most violence is confined to the east of the country where unemployment is high and Mr Gaddafi's grip said to be weaker. But they stressed that his regime had survived 41 years through brutality and he showed no signs of losing his nerve.

William Hague, Britain's Foreign Secretary, condemned Libya for firing on demonstrators. "This is clearly unacceptable and horrifying. Governments must respond to the legitimate aspirations of their people, rather than resort to the use of force, and must respect the right to peaceful protest."

However, experts admitted the British Government and business interests were watching the situation closely. BP declined to comment on the situation last night but said it was concerned for its 140 employees in Libya. Security experts said all UK companies in Libya had contingency plans if the uprising spread.

Douglas Alexander, the Shadow Foreign Secretary, said: "From Libya to Bahrain, many past assumptions have been dissolved by these demonstrations. Britain should speak out against violence, speak up for human rights in all countries and make clear that moves towards democracy are the best guarantee of long-term stability."

Critics claim that British economic interests in Libya had muted support for the uprising there. British exports to Libya have risen to more than £400m and are set to increase dramatically as oil and gas investments by Shell and BP develop. Britain halted military exports to Libya last week but sniper rifles, which may have killed protesters yesterday, were amongst equipment exported to Tripoli last year.

Protests have continued to grow in strength and violence after the first demonstration last Tuesday, when thousands massed following the arrest of a human rights campaigner.

A Benghazi cleric, Abellah al-Warfali, told al-Jazeera television he had a list of 16 people being buried yesterday, most with bullet wounds. "I saw with my own eyes a tank crushing two people in a car," he said. "They hadn't done any harm to anyone."

Several reports said government-recruited mercenaries were behind the worst violence including sniper attacks and the use of heavy machine guns. A British-based IT consultant, Ahmed Swelim, 26, originally from Benghazi, said relatives told him the situation had reached "critical point". "People are living in fear since he [Mr Gaddafi] brought in African mercenaries. They are dressing as normal people but doing random killings. They will shoot or cut people's hands off. The whole city is erupting. People went out to protest peacefully. They want an end to this oppression. The death toll is much higher than reported. There are more than 200 dead. My cousin, a doctor at a main hospital, has seen the bodies. There are more than 1,000 injured."

He said people in Benghazi were desperate. "We need an end to this oppression. It's been 41 years. We've been dreaming of this day. If we go back, the whole area will be wiped out. We know how crazy he is. If we step down, we will be taken out."

The Libyan regime has suppressed the internet. Technical experts reported that 13 globally routed links were withdrawn late on Friday. Foreign journalists are prevented from entering Libya and local reporters are barred from travelling to Benghazi. Al-Jazeera said its signal was being jammed on several frequencies. The state-run media defended the regime. The Al-Zahf Alakhdar (Green March) newspaper published an editorial entitled: "No leader except Gaddafi!" Elsewhere, the country appeared calm. A government-run newspaper blamed the protests on Zionism and the "traitors of the West". Officials said foreign media had exaggerated the violence.

Sir Richard Dalton, now of the foreign affairs think tank Chatham House, described it as the most serious crisis yet faced by Colonel Gaddafi. "It could be the regime is approaching a tipping point," he said. "We don't know what the willingness of ordinary Libyans will be to take such casualties without coming out in larger numbers.

"It's clear that it's a highly political revolution. It's not economic grievance, although that will be in the background. It's an extraordinary significant event for Libya." He warned that the security forces and protest groups both possessed "considerable capability for ruthlessness".

"It is too early to write off Gaddafi's regime because it is resilient and has a lot of people who will go to considerable lengths to maintain their positions," he said. Complaints about poor economic and social provisions such as education and health were of long standing he said.

"The ratio between risk and reward still points towards the risk being unacceptably high. In Egypt, when it was clear that the army wasn't going to use live ammunition, the perception of potential for success soared and a lot more people came out on to the streets. That could happen in Libya, but we're still some way from that point because the security forces are still willing to inflict considerable casualties."

He denied UK economic interests in the country would compromise the official response. "It is very much in the UK's political and security interest to work with Libya," he said.

Libya: 60 Years

1951 Gains independence under hereditary monarchy headed by King Idris

1969 Coup d’état led by 27-year-old army officer Muammar Gaddafi

1979 US declares Libya a state sponsor of terrorism

1981 Two Libyan jets are shot down after firing on a US military aircraft over the Mediterranean

1984 UK severs ties with Libya following the shooting of PC Yvonne Fletcher outside the Libyan embassy in London

1986 US applies economic sanctions; two US servicemen killed in a disco bombing in Berlin. US retaliates by bombing Tripoli and Benghazi, killing at least 100 people. Some of the 66 jets take off from British air bases

1988 Passenger airliner Pan Am flight 103 from Heathrow to New York explodes over Lockerbie in Scotland killing a total of 270 people

1989 French airliner UTA Flight 772 blows up over the Sahara Desert. Libyan agents are accused

1991 Libyan citizens Abdelbaset al-Megrahi and Lamin Khalifa Fhimah are indicted for the Lockerbie bombing

1992 UN imposes sanctions on Libya

1999 Libya pays compensation for the death of Yvonne Fletcher; UK diplomatic ties restored

2000 A deal sees the two men accused of the Lockerbie bombing stand trial in a special court in the Netherlands

2001 Megrahi is convicted of the bombing and sentenced to life imprisonment. Fhimah is acquitted

2003 Libya pays $3bn compensation to the relatives of the two airline bombings and renounces weapons of mass destruction

2004 Tony Blair visits Libya and shakes Gaddafi’s hand. Shell announces deal for oil and gas exploration off the Libyan coast

2008 Foreign and Commonwealth Minister Bill Rammell signs five agreements improving UK ties with Libya

2009 Megrahi is released on medical grounds and receives a hero’s welcome on his return to Libya

2011 UK revokes licences for arms sales to Libya following brutal suppression of anti-government protests