BENGHAZI: Production at Libya's giant Sharara oilfield was gradually restarting on Saturday after a blockade closed the 300,000 barrels-per-day field for more than four months, two engineers from the field said.

The restart at the field in southwest Libya followed a rapid military retreat by forces loyal to eastern-based commander Khalifa Haftar, whose allies had blockaded major oilfields and ports since January, shutting off most of Libya's production and billions of dollars in revenue.

A valve that had been closed on the pipeline running from Sharara to the northern port of Zawiya as part of the blockade was reopened on Friday, the Petroleum Facilities Guard said.

Ali Kanna, a guard commander aligned with the internationally recognised Government of National Accord (GNA), had entered Sharara without resistance on Saturday, the engineers said. GNA forces have been advancing from Tripoli towards the south and east as Haftar's forces retreat.

Output at Sharara began at about 20,000 bpd, and the filling of storage tanks during the restart was expected to take two to three days, the engineers said.

There was no immediate comment from Libya's National Oil Corporation (NOC), nor any news of a restart at El Feel, another southwestern field linked to Sharara.

Sharara is operated by the NOC in a joint venture with Spain's Repsol, France's Total, Austria's OMV and Norway's Equinor. The NOC declared force majeure on loadings from the field in January.

El Feel, which previously produced 70,000 bpd, is operated by the NOC and Italy's Eni.