Abuja (AFP) - Nigeria said Sunday it had carried out air strikes in the northeast of the country to repel an attack by Boko Haram and had killed a "large number" of the Islamist extremists.

The air raids came as Nigeria and its neighbours prepared to launch a new multinational force to combat Boko Haram, in the face of the group's escalating violence in the region.

The Nigerian Air Force said it had "successfully repelled an attack on Bita village by the Boko Haram terrorist group" in a combined operation with ground troops after spotting militants planning an assault.

"Consequently, a large number of the insurgents were killed and several others were injured," it said in a statement, without disclosing when the incident took place.

Boko Haram has staged a string of strikes -- often by female bombers -- targeting markets in Nigeria, Chad and Cameroon that have killed and wounded scores in the past month.

The new 8,700-strong multinational force -- made up of troops from Nigeria as well as Cameroon, Chad and Niger -- is expected to go into action soon, officials say.

Nigerian President Muhammadu Buhari, who won an election in March on a promise to defeat the jihadists, said Friday the new force would "lead to the speedy defeat and elimination of Boko Haram".

The group's bloody insurgency in Nigeria has left more than 15,000 people dead since 2009.