Libya's official news agency blames Israel for unrest, as security forces attack protesters.
Libyan leader Muammar Gaddafi has unleashed a bloody crackdown against pro-democracy protestors seeking his ouster, killing dozens of people in only four days of protests.
On Sunday, the unrest spread to capital Tripoli from the eastern port city Benghazi.
Libyan Internet activists have denounced the international community's failure to act over the "massacres" in Libya.
The Cairo-based Arab Organisation for Human Rights has decried the use of violence against the protestors in Libya and called for an international investigation. The Vienna-based Friends of Humanity said the Libyan regime's onslaught was tantamount to "war crimes".
There are conflicting reports on the death toll but it is generally believed to be in the hundreds now.
Human Rights Watch reports that 173 people had died prior to Monday. The London-based private newspaper Libya Al-Youm quoted a local doctor as saying that 285 people died in the eastern city of Benghazi alone.
Some 300 people have been killed in Benghazi, the country’s second largest city, witnesses told Al Jazeera by phone.
The crackdown by Gaddafi, who has ruled Libya since 1969, threatens to make the revolt the most costly in terms of human lives and bloodshed in the wave of demonstrations sweeping across the region for greater freedoms.
Gaddafi, trying to stave off the fate of the presidents of Tunisia and Egypt who were removed from power after facing similar protests, has resorted to much harsher military tactics than those used in uprisings in neighbouring Egypt or Tunisia.
His tactics include cutting off food, fuel and medical supplies as well as electricity to revolting cities. The regime also cut off most communications to try to make sure the unrest does not spread to other cities. But the move failed to prevent protests erupting in capital Tripoli on Sunday.
Pan-Arab news outlets report that Gaddafi's troops have used live ammunition and heavy military equipment such as anti-tank missiles in Benghazi. Late on Sunday fierce clashes were being reported in Tripoli.
Libya Al Youm reported on its website on Sunday that the regime was using "heavy weapons" and shooting at random. Read more.