Libyan forces killed three suspected Daesh fighters near an oilfield in the southeast of the country, a local official said on Saturday.
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 US 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.
In December, armed men blew up a Waha pipeline pumping crude to Es Sider port, temporarily cutting Libyan output by around 100,000 barrels per day. Officials blamed "terrorists", without giving details.
The area has poor security and sources say it has been populated by Daesh fighters since they lost control of their stronghold in Libya, the central city of Sirte, in 2016.