Two soldiers were also killed and five wounded during clashes over two days, one of which took place near the Dhahra oilfield on Saturday, said Umar al-Faqeh, head of the Maradah administration to which the area belongs. There had been fighting in another area on Friday, he added.
The Dhahra field is operated by Waha, a joint-venture between Libya's state National Oil Company and U.S. firms Hess, Marathon and ConocoPhillips.
The oil protection force guarding the Waha operations is allied to Libya's eastern government. The UN-backed administration is in the capital, Tripoli, in western Libya.
Libya has been mired in conflict since the toppling of long-time ruler Muammar Gaddafi in 2011.
The area has poor security and sources say it has been populated by ISIS fighters since they lost control of their stronghold in Libya, the central city of Sirte, in 2016.
(Reporting by Ayman al-Warfalli; Writing by Ulf Laessing; Editing by Andrew Bolton)
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