Libya's rebel leadership has had "no contact" with Shukri Ghanem, the Libyan oil minister who is thought to have defected, a spokesman said today.

"We have not had and do not have any contact with him," Jalal al-Gallal said on behalf of the rebel National Transitional Council..

"Maybe he is in Tunisia, as per media reports, but for now, he has not let us know that he wants to join us," the spokesman said.

Earlier, a Tunisian government official confirmed that Ghanem, also chairman of Libya's national oil company, crossed the border by car on Saturday and is staying in a hotel on the southern tourist island of Djerba.

If it is confirmed the minister has left his post, he would be among the most senior officials to abandon Libyan strongman Moamer Kadhafi's government since an uprising erupted in mid-February.

Former foreign minister Mussa Kussa defected to Britain in March, leaving Libya via Tunisia.

In April, the US Treasury Department froze the assets of five senior Kadhafi regime figures, including Ghanem, in a bid to fracture the veteran ruler's inner circle.

Libya is a key crude-exporting nation but its output has been slashed since the revolt began.

According to the International Energy Agency, Libya's exports averaged 1.49 million barrels per day (bpd) before the uprising, with 85 percent of that going to Europe. Output has fallen as low as 300,000 bpd during the insurgency, although rebels plan to ramp up production.

The European Union last month added to its Libya sanctions list 26 energy firms accused of financing Kadhafi's regime, a move that Germany said amounted to a de facto oil and gas embargo.