Libyan troops have opened fire with machine-guns and large-calibre weapons on anti-government protesters in the second city Benghazi, witnesses say.
An unknown number of people, including children, are said to have been killed.
Witnesses described scenes of chaos as snipers shot from the roofs of buildings and demonstrators fought back against troops on the ground.
A doctor at a local hospital said he and his colleagues were treating hundreds of injured protesters.
Reports are difficult to verify as Libyan authorities have not allowed foreign journalists into the country, but residents say Benghazi and another eastern city, al-Bayda, appear to be out of government control.
“Dozens were killed... not 15, dozens”
Eyewitness quoted by Reuters
Tripoli 'key' to events in Libya
There have been no reports of major protests in the capital Tripoli.
A Benghazi resident told the BBC that security forces inside a government compound had fired on protesters with mortars and 14.5mm machine guns - a heavy machine gun typically produced in the former USSR.
They were, he said, machine-gunning cars and people indiscriminately. "A lot [of people] have fallen down today," he added.
Other witnesses spoke of snipers firing at protesters from rooftops and there were widespread reports of foreign mercenaries from sub-Saharan Africa being brought in to attack protesters.
A doctor told the BBC that situation in the city was "like hell", saying he had been seeing people with gunshot wounds being carried into his hospital all day.
Full article in the link above. Sorry, I can't dress links, will someone help?
News of the World (its a piece of shit but its the first newspaper I saw this morning) reports a similar story but puts the death toll at 100 just from an assault by special forces on a protester encampment.
Edited link to dress it - SCRawl