Cameroonian troops have entered Nigeria for the first time in the war against Boko Haram, in an apparent change of tactics that comes as the terrorist group continues to lose territory and firepower.

A military official said on Monday that the Cameroonian assault on Boko Haram positions in the Nigerian village of Ndaba left several militants dead. They also destroyed equipment and prevented an insurgency attack on the village.

Cameroonian troops have not crossed the border in the two years that they have been at war with Boko Haram. Last week’s attack was surprising because militants were not planning an attack on Cameroonian territory.

The attack took place about 20 kilometres inside Nigeria on Thursday and Friday, said Col. Jacob Kodji.

Boko Haram is trying to create a caliphate to enforce strict Islamic laws in northeast Nigeria and parts of Cameroon. More than 15,000 people have died since the group began violence in 2009.

Last week’s cross-border attack by Cameroon came as the group continues to endure declining fortunes after opening up numerous battlefronts in Nigeria, Cameroon, Chad and Niger. Its announced alliance with ISIL does not appear to be translating into anything concrete on the ground.

Nigeria also announced on Monday that it had recaptured a town northeast of the country held by the militants for more than six week. “FLASH: Nigerian troops have this afternoon routed terrorists from Bama … Mopping up operation is on-going,” the Nigerian defence headquarters said via Twitter on Monday.

Nigeria says it had since January liberated 36 towns previously held by Boko Haram.