Libya's Shokri Ghanem, chairman of the country's National Oil Corporation, said on Thursday the North African nation's oil output had fallen to 250,000 to 300,000 barrels per day (bpd) from about 1.6 million.
"There is some production in Libya, around 250,000 to 300,000 barrels per day, which is being used domestically," he told Reuters.
Ghanem called the reported sale of Libyan oil by rebels fighting forces loyal to leader Muammar Gaddafi "very sad" and said it would only contribute to divisive tensions in the country.
"It does not help by disintegrating and dividing the country. We always wanted one country, one oil company," he said.
Ghanem also expressed concern about the potentially wider implications of an air strike on the Sarir oilfield which the Libyans have blamed on British warplanes.
"I have heard the news that the Sarir oilfield was bombed. This is very bad. ...It is near the Man-made River which supplies Libya with 70 per cent of its water."
Libya is a member of OPEC, Africa's third-largest producer and holder of the continent's largest crude reserves.
Prior to the current conflict, it supplied about two per cent of the world's oil.