Niger's defense ministry says soldiers have killed 38 Boko Haram Islamic extremists during an operation in the country's southeast Diffa region.

Col. Moustapha Michel Ledru said on national television late Friday that two Nigerien soldiers were wounded in the operation that had support from Chad's army.

Ledru on Tuesday said five soldiers and 30 Nigeria-based Boko Haram militants had been killed after an ambush by the extremists led to fighting Monday.

Boko Haram has killed some 20,000 and displaced millions in its seven-year insurgency. The Nigeria-based extremists have been launching attacks across the country's borders into Niger, Chad and Cameroon, which contribute to a multinational force that seeks to counter it.