19 Feb. From BBC News: New violence has been reported in Libya's second city, Benghazi, with troops said to have opened fire again on anti-government protesters.
At least 15 people were killed and many more wounded, unconfirmed reports say.
Witnesses described scenes of chaos as army snipers opened fire. Some reports spoke of missiles being fired.
At least 84 people had already died, rights groups say. Reports have been hard to verify amid tight controls on information and the internet.
US-based group Human Rights Watch said the 84 had died in Benghazi as well as in a number of other cities in eastern Libya.
The BBC's Middle East correspondent Jon Leyne says that for much of the day it seemed as if the government had lost control of the eastern cities of al-Badai and Benghazi. But residents always feared a major counter-assault and it seems it may have begun. Reports emerging from Libya are sketchy and sporadic, after the government moved to control internet access, but the Associated Press news agency and al-Jazeera television both said troops had opened fire on people attending a funeral on Saturday, killing 15.
Citing witnesses and medical staff in Benghazi, the reports told of snipers firing on crowds gathered to mourn some of those killed on Friday.
One doctor told the BBC that situation in the city was "like hell".
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"I have been seeing injured people being carried in all day. They have been shot in the head and chest. They have broken arms and legs. There is shooting going on everywhere," said the doctor.
He also suggested that foreign mercenaries from sub-Saharan Africa - paid by the Libyan government - had been brought in to attack protesters.
Another resident told the BBC that 40 people had been killed in a short space of time.
"Please, please tell the world that [Gaddafi] is killing the people for no reason. They're very peaceful protesters," he said. "He's bringing foreigners from nowhere, Africans, black African snipers shooting the people in the streets of Benghazi, now he's attacking Benghazi itself with rocket missiles."
Another eyewitness, named only as Ahmed, told al-Jazeera the killing in Benghazi was unprecedented.
"We've never heard of anything like this before. It's horrible," he said.
'Unacceptable and horrifying'
Benghazi, which is about 1,000 km (600 miles) from the capital, Tripoli, has been the main focus of the demonstrations against Col Muammar Gaddafi's 42-year rule. State media had warned of retaliation if the unrest continued.
But although unrest has spread to other towns and cities, there have been no reports of major protests in Tripoli.
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Media restrictions make it difficult to verify reports independently but the BBC has confirmed that websites including Facebook and al-Jazeera Arabic were blocked on Saturday.
Despite the drop-off in internet traffic, social networks including Twitter were awash with reports of events in the city.
One protester told the BBC that those rallying in Benghazi would stand firm.
"We have no choice. We have been suffering for 42 years and we are not going," she said.
UK Foreign Secretary William Hague said reports of heavy weapons and sniper fire being used on protesters were unacceptable.
"This is clearly unacceptable and horrifying," Mr Hague said.
Security forces opened fire in Benghazi on Friday when protesters approached a compound used by Col Gaddafi when he visits the city, eyewitnesses say.
The city's al-Jala hospital received the bodies of 35 people killed in the shooting, according to Human Rights Watch (HRW) and media reports.
Amid the crackdown, the semi-independent Quryna newspaper reported that the government would replace many state executives and decentralise and restructure the government.
It was unclear whether the political move was in response to growing unrest.
Earlier, the pro-government Al-Zahf Al-Akhdar newspaper threatened that the authorities would "violently and thunderously respond" to the protests.
Col Gaddafi is the Arab world's longest-serving leader, having ruled oil-rich Libya since a coup in 1969.
Libya is one of several Arab countries to have experienced pro-democracy demonstrations since the fall of long-time Tunisian President Zine El Abidine Ben Ali in January. Egypt's Hosni Mubarak was forced from power on 11 February.
The British Foreign Office is now advising UK citizens against all but essential travel to Benghazi, Ajdabiya, al-Bayda, al-Marj, Darnah, Ajdabiya, Tobruk and areas bordering Sudan, Chad, Niger and Algeria.
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