Prime Minister Haider al-Abadi of Iraq announced the recapture of Al Nuri Grand Mosque in Mosul on Thursday from Islamic State militants, calling it a sign of the end of the extremists’ grip on the region and vowing to chase them out of the country.

“We are seeing the end of the fake Daesh state, the liberation of Mosul proves that,” Mr. Abadi said on Twitter, using the Arabic acronym for the Islamic State. “We will not relent. Our brave forces will bring victory.”

Mosul has still not been entirely wrested from Islamic State control despite a complex eight-month battle for the city. But Thursday’s announcement signified a further push to eliminate the group.