The news agency, which has links to the militia-backed government in Tripoli that is not recognised by the international community, added that it was a suicide attack.
"Fifteen people were also wounded (...) among them women and children," it reported, quoting local and medical sources in Derna.
The attack came after clashes between local militiamen controlling the city and Islamic State group fighters.
Libya descended into chaos after a revolt unseated longtime dictator Moamer Kadhafi in 2011. It now has rival governments and parliaments, as well as powerful militias battling for influence and a share of its oil wealth.