Security forces loyal to Libya's Moammar Gadhafi unleashed heavy gunfire Sunday on thousands marching in the rebellious eastern city of Benghazi, cutting down mourners trying to bury victims.

More than 200 people in Libya have been killed in the fiercest crackdown yet since uprisings began in parts of the Arab world.

The Libyan leadership was defiant but admitted mistakes early Monday, even as protests were reported to have spread to Tripoli, the capital.

One of Gadhafi's sons, Seif al-Islam, warned in a nationally televised address that continued anti-government protests might lead to a civil war that could send the country's oil wells up in flames.

Appearing on Libyan state television, he said the army still backed his father, who was leading the fight, although he added that some military bases, tanks and weapons had been seized.

"We are not Tunisia and Egypt," the younger Gadhafi said, referring to the successful uprisings that toppled longtime regimes in Libya's neighbours.

Son says death toll exaggerated

He acknowledged that the army made mistakes during protests because it was not trained to deal with demonstrators but added that the number of dead had been exaggerated, giving a death toll of 84. Human Rights Watch put the number at 174 through Saturday, and doctors in Benghazi said more than 200 have died since the protests began.

The younger Gadhafi offered to put forward reforms within days that he described as a "historic national initiative" and said the regime was willing to remove some restrictions and begin discussions for a constitution. He offered to change a number of laws, including those covering the media and the penal code.

In one Benghazi hospital, a doctor said 15 people died in Sunday's clashes, speaking on condition of anonymity for fear of reprisals. Earlier he said his morgue had received at least 200 dead from six days of unrest.

The doctor said his hospital, one of two in Libya's second-largest city, is out of supplies and cannot treat more than 70 wounded in similar attacks on mourners Saturday and in other clashes.

"I am crying," the doctor said. "Why is the world not listening?"

Eyewitness reports trickling out of the country, where the internet has been largely shut down  and journalists cannot work freely, suggested that protesters were fighting back more forcefully against the Middle East's longest-serving leader.

'A state of war'

Benghazi is "in a state of war," said Mohamed Abdul-Rahman, a 42-year-old merchant, who described how some protesters burned a police headquarters.

A man shot in the leg Sunday said marchers were bearing coffins to a cemetery when they passed a Gadhafi compound in Libya's second-largest city. The man said security forces fired in the air and then opened up on the crowd.

Witnesses told The Associated Press a mixture of special commandos, foreign mercenaries and Gadhafi loyalists went after demonstrators on Saturday with knives, assault rifles and heavy-calibre weapons.

The violence followed days of protests in Benghazi, a focal point of the uprising aimed at toppling Gadhafi after more than 40 years of rule.

Libya's rebellion by those frustrated with Gadhafi's authoritarian regime has spread to more than a half-dozen cities, but Benghazi has been at the centre of unrest.

First defection

In the first-known defection from Gadhafi's regime, Libya's representative to the Arab League said he resigned his post to protest his government's decision to fire on demonstrators in Benghazi, the country's second largest city. A major tribe in Libya was also reported to have turned against Gadhafi.

In Tripoli, a Gadhafi stronghold, there have been few reports of protests. Secret police were heavily deployed on the streets of the city of two million to quickly put down any demonstrations.

On Sunday, however, armed security forces were seen on rooftops surrounding central Green Square in Tripoli, a witness said by telephone, speaking on condition of anonymity for fear of reprisal. The witness added that about 200 lawyers and judges were protesting inside a Tripoli courthouse, which was also surrounded by security forces.