It has been under the control of the militant group since last year
A US-backed Libyan militia say they have seized control of the headquarters of the Islamic State in the city of Sirte.
A spokesman for forces loyal to Libya's UN-backed government of national accord said the Ouagadougou Convention Centre is in their control.
The Mediterranean coast city is seen as IS's most significant stronghold in Libya.
It has been under the control of the militant group since February last year.