The spokesman for Libyan forces loyal to a U.N.-brokered government says his troops have advanced deep inside the coastal city of Sirte, the main stronghold of the Islamic State group's local affiliate.

Brig. Gen. Mohammed al-Ghasri tells The Associated Press that forces have seized a key bridge inside the city where the extremists used to hang the bodies of their enemies.

He says his forces are only five kilometers (three miles) from the city center and a key square called Zafrana, where IS killed prisoners. The fighting on Wednesday killed five of his fighters and wounded another 25.

Sirte is the only IS-held city outside Syria and Iraq, and was seen by some as a fallback option for the capital of its self-styled caliphate.