Nigerien special forces prepare to fight Boko Haram in Diffa (March 2015). (GALLO IMAGES/REUTERS)

Nigerian troops have killed 75 Boko Haram militants in 17 encounters in the restive northeast region in June, an official said on Sunday.

John Enenche, spokesman for the Nigerian military, said in a statement that the troops of Operation Lafiya Dole, while causing high casualties on the Boko Haram, also have rescued 35 captives from the militants, including 18 women and 16 children, in the encounters from June 1 to June 30.

One officer were killed while one soldier was wounded in action, according to Enenche.

Enenche said four insurgents including two women were captured during the period.

He said the military high command encourages the troops to remain resolute in curtailing the activities of terrorists in the northeast region of the country, and urges local communities to continue providing timely information to troops on activities of the Boko Haram militants for prompt and effective action.

Boko Haram launched a bloody insurgency in 2009 in northeastern Nigeria but later spread its atrocities to other countries in the Lake Chad region, which prompted a united military response.

Thousands of people have been killed and millions others displaced in the over-a-decade Boko Haram violence in Nigeria and neighboring countries.