Dozens of people were killed when Libyan troops used heavy weapons during a funeral procession amid unrest in Benghazi, a doctor in the city says.
She told the BBC that at least 45 bodies and 900 wounded had been brought to just one hospital on Saturday, describing the scene as a “massacre”.
Human Rights Watch says at least 173 people have been killed in Libya since demonstrations began on Wednesday.
Benghazi has been a leading focus of protests against Col Gaddafi’s rule.
Libya is one of several countries in the region to have seen pro-democracy campaigns 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.
BBC Middle East correspondent Jon Leyne says the current unrest in Libya is the most serious challenge to Col Muammar Gaddafi in his four decades in power.
Reports are difficult to verify as the Libyan authorities have imposed severe media restrictions.
The Benghazi doctor told the BBC that at least 45 bodies and 900 injured people had been brought to Jala hospital – most of them with gunshot wounds.
“Ninety percent of these gunshot wounds [were] mainly in the head, the neck, the chest, mainly in the heart,” she said.
She added that she has been in contact with other Benghazi hospitals, which she says were overwhelmed by casualties and have not been able to count the dead.