A spokesman for militias loyal to Libya's U.N.-brokered government say Islamic State militants have barricaded themselves in the center of their stronghold in the coastal city of Sirte, hoping to draw their attackers into a protracted street battle.

Brig-Gen. Mohammed al-Ghasri said Sunday the militants have barricaded themselves in a densely built-up area and their snipers have taken positions on rooftops waiting for the militias to advance. He says that IS suicide bombers are likely to target the militias if they close in on the area.

The militias have been shelling the area with artillery.

IS took over Sirte last year, exploiting Libya's turmoil to gain a foothold in the North African country. The fight to retake it is led by militias from the western city of Misrata.