MAIDUGURI, Nigeria (AP) — The Nigerian military says that an air force helicopter crashed in combat, as fighting raged against Boko Haram extremists for control of the strategic northeastern town of Baga.

Air Commodore Ibikunle Daramola tweeted that the helicopter crash occurred Wednesday. He said the fighting was at Damasak in Northern Borno state.

The military is fighting to regain control of Baga, which Boko Haram seized last week. The town is a key base for a multinational force fighting the extremists. Many Baga residents have fled to Maiduguri.

Baga, close to the border with Chad, has weapons, ammunition and other equipment are a key target for the extremists.

In addition to the fighting around Baga and the helicopter crash, 53 police are missing after a Boko Haram raid last week.