Extremists in Nigeria have begun using drones, the country’s president says, opening a worrying new front in the region’s nearly decade-long fight against Boko Haram, an offshoot linked to the Islamic State.

President Muhammadu Buhari announced the development during a meeting of countries contributing troops to a multinational force combating the extremists.

Deadly attacks against Nigeria’s military are on the rise. The military says 39 soldiers have been killed this month alone, with another 43 wounded.

Nigeria’s president says the extremists’ use of drones for surveillance in northeastern Nigeria has proven to be a “critical factor” in the resurgence of attacks.

Nigeria’s military has armed drones as the United States and others increasingly use them in West Africa’s fight against groups linked to al-Qaida and IS.