Nigeria on Monday said it had retaken Gamboru and four other towns held by Boko Haram following a joint weekend offensive by its military, civilian vigilantes and forces from neighbouring Chad and Cameroon.

"Our troops are in control after operations which had the active support of volunteers (vigilantes) and our friendly neighbours," national security spokesman Mike Omeri told AFP.

In a separate statement, he listed the towns in northeast Borno state retaken over the weekend as Mafa, Mallam Fatori, Abadam, Marte and Gamboru, where Chad has carried out three days of airstrikes.