Islamic State on Tuesday claimed responsibility for the suicide attack on the Tripoli headquarters of the Libyan state oil company that occurred the day before, according to SITE, a U.S.-based intelligence group that monitors extremists.
Two staffers at the National Oil Corporation were killed and 10 were wounded. The three attackers were also killed.
A statement from Amaq, the IS news agency, said it targeted the "economic interests of the pro-Crusader governments of the tyrants of Libya."
The U.N. mission in Libya condemned what it called a "cowardly terrorist attack."
Libya has been in nonstop political and social turmoil since longtime dictator Moammar Gadhafi was toppled and killed in 2011.
A rival government is jockeying for power with a U.N.-installed administration in Tripoli, which is struggling to assert its authority across the country.
Extremists, including Islamic State militants, claim to have a number of so-called "sleeper cells" inside Libya.