Libya's state-owned National Oil Corporation (NOC) has suffered losses of more than $3.5bn because of the forced closure of major oil sites since mid-April.

In a statement, NOC declared a state of “force majeure" at some facilities.

"After the expiry of the 72 hours and the loss of more than LD16bn, the NOC has decided to declare a state of force majeure" on the facilities in the Gulf of Sirte, it said.

The company had previously warned that it would be forced to declare "force majeure" within three days if production and export did not resume in the terminals of the Gulf of Sirte.

NOC chairman Mustafa Sanalla said: “We are forced to declare force majeure on the terminals of al-Sidra and Ras Lanouf, and on the field of Al-Fil.”

The oil company said production had “fallen sharply” and exports had dropped to between 365,000 barrels a day (b/d) and 409,000 b/d, a loss of 865,000 b/d compared to the average production before the crisis.

It also said that it was losing 220 million cubic metres a day (mcf/d) of gas.

The decline in gas production is contributing to chronic power cuts in the North African country.