Six US air strikes on an ISIL desert camp in Libya killed 17 fighters and destroyed three vehicles, the first American attack in Libya since President Donald Trump took office in January.
US Africa Command said in a statement on Sunday that strikes on Friday targeted a camp 240km southeast of Sirte, a city that was once the Islamic State of Iraq and the Levant stronghold in Libya.
The camp was used to move fighters in and out of Libya, plot attacks and store weapons, the statement said.
"ISIS and al-Qaeda have taken advantage of ungoverned spaces in Libya to establish sanctuaries for plotting, inspiring and directing terror attacks," it said, using another acronym for ISIL.
The strikes were carried out in coordination with Libya's Government of National Accord, it added.
A US official, speaking on condition of anonymity, said the air raids were carried out by armed drones.
The last-known US strike in Libya was on January 19, a day before Trump's inauguration, when more than 80 ISIL fighters, some believed to be plotting attacks in Europe, died in US air strikes on camps outside Sirte.
That attack was led by two B-2 bombers, which dropped about 100 precision-guided munitions on the camps.
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ISIL took over Sirte in early 2015, turning it into its most important base outside the Middle East and attracting large numbers of foreign fighters to the city. The group imposed its hard-line rule on residents and extended its control along about 250km of Libya's Mediterranean coastline.
But it struggled to keep a footing elsewhere in Libya and was forced out of Sirte by last December after a six-month campaign led by brigades from the western city of Misrata and backed by US air strikes.
ISIL has shifted to desert valleys and inland hills southeast of Tripoli as it seeks to exploit Libya's political divisions after their defeat in Sirte.
The United Nations launched a road map on Wednesday for a renewed international effort to break a political stalemate in Libya and end the turmoil that followed the country's 2011 uprising.
The UN-backed Government of National Accord established under a December 2015 deal never fully materialised in Tripoli, leaving Libya with three competing governments aligned with rival armed alliances.