Western countries, the European Union and United Nations have imposed sanctions on Libya and frozen government assets in the aftermath of an uprising which erupted last month against the long-term rule of Muammar Qaddafi.

Eni could not be immediately reached for comment.

Eni, whose chief executive called on Europe on Wednesday to lift sanctions against Libya, is loading oil from the western terminal of Bouri, which is under control of Qaddafi, fighting rebels for control of the world No.12 oil exporter.

“It is true but it was an exceptional case. Production is practically at zero,” one of the sources said referring to oil and gas fields Eni operates in Libya.

On Thursday, Qaddafi’s troops pushed forward toward the rebels stronghold of Benghazi and launched air raids on its outskirts as momentum gathered in support of air raids to stop government forces.

Major US oil companies including Exxon Mobil and ConocoPhillips have halted trade with Libya and banks are declining to clear payments in dollars.

The sources said the tanker can carry up to 600,000 barrels of crude oil and was due to pick up its cargo on Thursday.

Libya’s 1.6 million barrel a day oil exports have come to a virtual standstill in recent days due to the heavy fighting between rebel and Qaddafi forces.

Eni is the biggest foreign player, with billions of dollars invested in Libya. Italy was buying 500,000 barrels per day, or 22 percent of its oil, from Libya before sanctions and fighting stopped exports.