A Cameroonian soldier and an officer were killed on Wednesday when their vehicle ran over a roadside bomb in the Far North region, where the army is battling Nigeria's Boko Haram militants, a senior officer said.

"Unfortunately we lost two men. One was a captain," the officer said by phone from Maroua.

Boko Haram, whose six-year campaign to establish an Islamic emirate in northeast Nigeria has spread into neighbouring Cameroon, Chad and Niger, have started using landmines and roadside bombs as the armies of the four nations step up the fight to contain them.

The Cameroonian officer said the explosives probably came from a stock that Boko Haram stole last May when they attacked a Chinese workers' camp in Waza. The insurgents kidnapped 10 Chinese citizens and seized a large amount of explosives.