Since late January, Islamic State militants have carried out attacks, including a car bombing and siege at the Corinthia, a luxury hotel in Tripoli, and an attack on the Mabruk oilfield south of Sirte, according to a report circulated this week by the State Department’s Diplomatic Security Bureau.
The militants also posted on the web images of the beheading of 21 abducted Egyptian Coptic Christians on a Libyan beach.
The US State Department document said estimates of the number of Islamic State fighters operating in Libya ranged from 1000 to 3000.
Around 800 fighters were based in the Derna area alone, the report said, including up to 300 who previously fought in Syria or Iraq.
US agencies are evaluating evidence that appears to tie Islamic State to the militants who killed 20 foreign tourists on Wednesday at a museum in Tunis, the capital of Libya’s western neighbor Tunisia.