The chairman of Libya's National Oil Corporation has defected from Muammar Gaddafi's administration and fled to neighbouring Tunisia, a Tunisian security source said on Tuesday.
Libyan rebels also said they had information that Shokri Ghanem, 68, had defected, a move that if confirmed would deal a blow to Gaddafi's efforts to shore up his 41-year-rule.
"He is in a hotel with a group of other Libyan officials," the Tunisian source said. Another Tunisian security source said he was en route to the capital Tunis. The Libyan government made no comment.
Rebels hold Benghazi and the oil-producing east of the North African country, helped by a NATO bombing campaign sanctioned at the United Nations to protect civilians.
But the military victory rebels once sought seems a distant prospect and many pin their hopes on a collapse of central power in Tripoli driven by defections and disaffection.
Rebel finance and oil minister Ali Tarhouni told Reuters on a visit to Doha that he understood Ghanem had left his post.
Tarhouni said he hoped to represent Libya at an OPEC meeting in June. Since the start of unrest three months ago, Libya is estimated to have lost two thirds of its oil output.
Rebels and Arab media reported on a previous occasion that the U.S.-educated Ghanem had stepped down but he later re-appeared and said he was in his office and working as usual.
Russia hosted a representative of Gaddafi's government in Moscow on Tuesday. It called on Tripoli to stop using force against civilians, comply fully with U.N. Security Council resolutions and withdraw armed groups from cities.
"The answer we heard cannot be called negative," Foreign Minister Sergei Lavrov told reporters. He suggested Gaddafi's government was making such steps conditional on NATO and rebels calling a halt to the use of force.
Libya was ready to look at peace proposals based on those suggested by the African Union and to comply with Security Council resolutions, he said.
"The only things that our interlocutors from Tripoli noted today was the necessity of the insurgents accepting analogous steps and that NATO also stopped bombing," Lavrov said, adding that it remained to agree terms and a timeframe for a truce.
However, both the rebels and Western nations have rejected past ceasefire proposals, saying the only deal they would accept was one under which Gaddafi relinquished power. The proposal set out by the Russian foreign minister made no mention of that.
The talks indicate Russia's desire to act as peace maker and preserve its influence in Libya, where it has billions of dollars of arms, energy and infrastructure deals.
The International Criminal Court's prosecutor sought on Monday an arrest warrant for Gaddafi, accusing him of killing protesters. Gaddafi says his military campaign is directed only against Islamist militants, mercenaries and criminals.
Prosecutor Luis Moreno-Ocampo also asked judges for the arrest of Gaddafi's son Saif al-Islam and his spy chief brother-in-law Abdullah al-Senussi.
Moreno-Ocampo said Tripoli had attacked residential buildings, suppressed protests with live ammunition, used heavy artillery against funeral processions and deployed snipers to kill people leaving mosques after prayers.
NATO, which has been hitting targets in Libya for nearly two months, appeared to step up its bombing campaign on Monday with strikes in several towns and cities including Tripoli, according to Libyan state television and rebels.