A Nigerian Air Force helicopter crashed in combat, as fighting raged against Boko Haram extremists for control of the strategic town of Baga in northeastern Nigeria, according to the military.The helicopter crash occurred on Wednesday, according to a tweet by air force spokesperson, Air Commodore Ibikunle Daramola.The fighting was at Damasak in Northern Borno state, he said, without giving details of the fate of the helicopter crew.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 the larger city of Maiduguri.The fighting for Baga is intense, the chief of army training and operations, Major General Lamidi Adeosun, told reporters."It's a ding-dong situation but we are engaging them," he said last week. "We are not in total control but Boko Haram have not taken control of Baga, either."Baga, close to the border with Chad, has weapons, ammunition and other equipment are a key target for the extremists. Insurgents also overran the base in 2015.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. The Islamic State West Africa Province, the largest ISIS-linked extremist group in Africa, claimed to kill or wound "dozens" of soldiers in the latest attack, according to the SITE Intelligence Group that monitors extremist communiques.Nigeria's military rarely announces death tolls in such attacks, but the government in November acknowledged dozens of soldier deaths in what it called an extremist resurgence.In addition to the fighting for Baga and the helicopter crash, 53 police are missing after a Boko Haram raid last week.It is not known if the missing police are dead, captured or escaped alive, according to a senior police officer in Maiduguri, who spoke on condition of anonymity because he is not authorized to speak to the press. Among the missing are 40 marine police who were patrolling Lake Chad, he said.Nigeria's Defence Minister Mannir Dan-Ali reiterated the military's commitment to ending Boko Haram's insurgency in the country. He was speaking to the press Wednesday while on his way to neighboring Chad to discuss Boko Haram activity in areas along the border between the two countries.Dan -Ali was responding to recent attacks by Boko Haram on Nigerian military in the northern parts of Borno State, including Baga and others towns. He met with Nigerian military commanders for about an hour.The government also last month confirmed the insurgents had begun using drones, calling it a "critical factor" in the rise in attacks. Buhari at the time held an urgent meeting with member countries to "enhance the capacity" of the multinational force.The nearly decade-old Boko Haram insurgency has been blamed for some 20,000 deaths and thousands of abductions. The unrest and displacement of millions of hungry people have turned northeastern Nigeria into one of the world's worst humanitarian crises.