TRIPOLI (Reuters) – Libya's veteran ruler, Muammar Qaddafi, faces one of his severest challenges amid protests by thousands in the second city of Benghazi and reports that more than 40 people have been killed by security forces.

The demonstrations on Friday against his four decades in power were unprecedented with Amnesty International saying 46 people had been killed in a three-day crackdown.
Any funerals of dead protesters could act as further flashpoints for demonstrators emboldened by uprisings in neighboring Tunisia and Egypt that toppled long-ruling presidents.
""Special forces who have a very strong allegiance to Qaddafi are still fighting desperately to gain to control, to gain ground and the people are fighting them street by street,"" said a resident of Benghazi identified as Mohammed by the BBC.
The broadcaster said residents in Benghazi reported there was no electricity in parts of the city and that tanks were stationed outside the court building.
While the level of unrest has not previously been seen before in the oil exporter, Libya-watchers say the situation is different from Egypt, because Qaddafi has oil cash to smooth over social problems.
Qaddafi is also respected in much of the country, though less so in the Cyrenaica region around Benghazi.
""For sure there is no national uprising,"" said Noman Benotman, a former opposition Libyan Islamist who is based in Britain but is currently in Tripoli.
""I don't think Libya is comparable to Egypt or Tunisia. Qaddafi would fight to the very last moment,"" he said by telephone from the Libyan capital.
The BBC quoted one Benghazi protester as saying some soldiers had switched sides and that people clambered unopposed on to three tanks.
""The soldiers say we are citizens of this country and we cannot fight our citizens,"" he said.
Tight government control and media restrictions have limited the amount of information emerging about the unrest.
Qatar-based news channel Al Jazeera said its signal was being jammed on several frequencies and its website had been blocked in Libya.
Amnesty quoted sources at a hospital in Benghazi, the focus for the violence and about 1,000 km (600 miles) east of Tripoli, as saying the most common injuries were gunshot wounds to the head, chest and neck. Officials have given no death toll, or commented directly on the unrest.
""This alarming rise in the death toll, and the reported nature of the victims' injuries, strongly suggests that security forces are permitted lethal use of force against unarmed protesters calling for political change,"" Amnesty said.
Eastern Libya focus of protests
The privately owned Quryna newspaper said that in Benghazi thousands of residents had gathered on Friday for the funeral processions of 14 protesters killed in clashes there. Thousands more had demonstrated in front of Benghazi court building.
Opposition activists said protesters fought troops for control of the nearby town of Al Bayda, scene of some of the worst violence over the past two days, where townspeople said they were burying 14 people who were killed in earlier clashes.
Residents said that by Friday evening the streets were calm but there were conflicting accounts about whether opposition activists or security forces were in control of the town.
Ashour Shamis, a London-based Libyan journalist, said protesters had stormed Benghazi's Kuwafiyah prison and freed dozens of political prisoners. Quryna said 1,000 prisoners had escaped and 150 had been recaptured.
The unrest though was not on a national scale with most protests confined to the east around Benghazi, where support for Qaddafi has traditionally been weak. There were no reliable reports of major protests elsewhere, and state media said there had been pro-Qaddafi rallies in the capital.