SIRTE, Libya/WASHINGTON (Reuters) - The U.S. military conducted air strikes on Monday targeting Islamic State militants in the Libyan city of Sirte, the Pentagon said in a statement.

Forces aligned with the United Nations-backed government have been battling Islamic State in Sirte since May.

Islamic State still holds several strategic sites in central Sirte, including the university, the main hospital and the Ouagadougou conference hall, where fighters believe they have stocked large quantities of ammunition and provisions.

Libya's Government of National Accord (GNA) requested the U.S. air strikes in Sirte, and President Barack Obama approved them, Pentagon spokesman Peter Cook said in a statement.

"GNA-aligned forces have had success in recapturing territory from ISIL thus far around Sirte, and additional U.S. strikes will continue to target ISIL in Sirte in order to enable the GNA to make a decisive, strategic advance," Cook said, using an acronym for Islamic State.

Libyan Prime Minster Fayez Seraj said in a statement broadcast on state television that the air strikes caused "severe losses to enemy ranks."

(Reporting by Yeganeh Torbati and Idrees Ali in Washington and Ahmed Elumami in Tripoli; Additional reporting by Goran Tomasevic in Sirte; Editing by Jonathan Oatis)