BBC: Pro-Gaddafi tanks are inside Libya's rebel stronghold of Benghazi, a BBC journalist has witnessed, as the city came under attack.
A jet appears to have been shot down over the city in spite of a declared ceasefire and a UN no-fly resolution.
World leaders are due to meet in Paris to discuss military action.
The rebel leader has appealed to the international community to stop the pro-Gaddafi bombardment, but the government denies claims of attacks.
"Now there is a bombardment by artillery and rockets on all districts of Benghazi," Mustafa Abdul Jalil told Al Jazeera television. "There will be a catastrophe if the international community does not implement the resolutions of the UN Security Council.
"We appeal to the international community, to the all the free world, to stop this tyranny from exterminating civilians."
UN Secretary General ban Ki-moon says the world must "speak with one voice" on Libya.
The new UN resolution authorised "all necessary measures" to protect Libyan civilians. (+ video) » | Saturday, March 19, 2011
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