He said the bombardment seemed to have come from the direction of the sea. This could not be confirmed and there were no further details of the attack. A warplane was circling over Ras Lanuf, the Reuters witness said.

Earlier, rebels fired rockets out to sea after reports that Libyan gunboats in the Mediterranean may have attacked rebel positions on the front line in the oil-producing east.

A counter-offensive by forces loyal to Gaddafi has halted the rebels' advance along Libya's eastern coast, where they have been forced to withdraw from the strategic town of Bin Jawad after coming under heavy fire.

Dr. Gebril Hewadi of the Benghazi medical management committee told Reuters television at least 400 people had been killed in eastern Libya since clashes began there on Feb. 17, with many corpses yet to be recovered from bomb sites.Meanwhile, Russia will ban all weapons sales to Libya, the Kremlin said in a statement on Thursday, effectively suspending its arms contracts with Gaddafi's government.

NATO and the European Union were set to begin two days of talks on Libya focusing on a possible "no-fly" zone after some of the fiercest fighting on the ground in almost three weeks of clashes.

Meanwhile, Germany joined other countries in imposing financial measures on the Libyan government.