According to local eyewitnesses and sources, cited by Reuters, the car bombs targeted a military unit called Bulahati belonging to the eastern forces of the Libyan National Army (LNA) in the city centre.
Derna, once a militant stronghold, is about 292 km (182 miles) distant from Libya's second city, Benghazi, and was reportedly declared to be under the complete control of Khalifa Haftar's LNA in June 2018.
Derna was reportedly the first city outside Syria or Iraq to fall to the Daesh group.
The instability also resulted in the rise of terror groups such as *Daesh. Libyan armed forces have been fighting the Islamist insurgency which swept the country after its longtime ruler Muammar Gaddafi was toppled in 2011.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia and many other countries.