The U.S. Treasury Department has issued sanctions against the leader of a Libyan militia for directing attacks on oil facilities in the country.

In a statement on Wednesday, the department accused Ibrahim Jathran of destroying peace and stability in Libya by overseeing forces that attacked Libyan oil facilities in the “oil crescent,” a lucrative target for rogue militias and criminals.

The department said the militia had caused many fatalities in Libya this year.

“Jathran’s repeated militia attacks on Libya’s oil facilities have done colossal damage to its economy and robbed the Libyan people of billions of dollars in oil revenue,” said Sigal Mandelker, Treasury undersecretary for terrorism and financial intelligence.

He said Jathran’s attacks have affected Libyan oil exports since 2013.

Forces led by Jathran violently attacked and seized control of the Libyan oil ports Ras Lanuf and Al Sidra in June, the department said, costing Libya more than 1.4 billion dollars in revenue and setting back efforts to promote political progress and stability.

The UN Security Council Libya sanctions committee blacklisted Jathran on Tuesday, subjecting him to a global asset freeze and travel ban.

Jathran is sought by judicial authorities in Tripoli for blockades of oil terminals and attempts to export oil independently.

Libya, which has been in turmoil since a 2011 uprising that toppled Muammar Gaddafi, has been divided between rival governments and military factions based in the east and west of the country since 2014, causing political deadlock and an economic crisis.

Armed groups regularly block oilfields to make demands. Several armed men attacked the headquarters of Libya’s National Oil Corporation in the capital Tripoli on Monday, killing at least two staff members, a security official said.

No group immediately claimed responsibility for the attack.