TRIPOLI (Reuters) - Libya’s El Sharara oilfield, the country’s biggest, remains closed because an armed group is still there, the chairman of state oil firm NOC said on Sunday.

Mustafa Sanalla rebuffed calls by eastern Libyan forces called Libyan National Army (LNA), which had taken control of the 315,000 barrels a day field and declared it secure.

“The field is closed because of the presence of a group of civilians, this armed militia, and some military people with them,” the NOC chairman said in the video posted online.

The oilfield deep in Libya’s south has been closed since December when state guards and tribesmen seized it to make financial demands, the latest in several such closures over the past few years.

In January, the LNA, which is based in eastern Libya, started an offensive to secure El Sharara and nearby El Feel oilfields and fight militants in the south.

In February it sent a force to the field and last week handed control of it to the same oil security force that had been responsible for the closure, after holding negotiations with them over their demands.

The LNA later called on NOC to lift force majeure, a contractual waiver declared in December.

But Sanalla said NOC’s conditions for such a move, including safety for its workers and the departure of the armed group responsible for the field’s closure, had not yet been met.

“The field is not yet safe,” he said.

Sanalla said NOC was in contact with the LNA force, saying the state oil firm was neutral and dealt with all parties in Libya’s conflict, explaining his contact with the LNA.

He referred to the LNA as “army” as it is known in eastern Libya, the power base of its commander Khalia Haftar.

Haftar’s LNA control the east and have started an offensive in southern Libya. It is allied to a parallel government based in the east opposing the U.N.-backed administration in Tripoli where NOC is based.

The LNA already secures oil ports in eastern Libya and last week also claimed control of the El Feel oilfield, which produces around 75,000 bpd.