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 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.

An AFP journalist in Fotokol, a Cameroonian town less than one kilometre (mile) from Gamboru, said the aerial bombardment of the area was ongoing earlier Monday but the situation appeared quiet by the evening.

Boko Haram had for many months been in control of a series of towns along Nigeria’s northeastern border and staged a string of cross-border attacks, especially inside Cameroon.

There had been growing calls for the affected countries to mount a joint offensive amid evidence that Boko Haram was rapidly growing in strength.

The new multi-lateral offensive may succeed in further weakening Boko Haram but there could also be political consequences for Nigerian President Goodluck Jonathan, who faces a tough re-election test in less than two weeks.

Nigeria’s willingness to allow foreign militaries to bomb its own territory and possibly occupy areas with ground forces has been seen as an embarrassment by some in Africa’s most populous and top economy.

Omeri’s statement also said 11 towns in Adamawa state to the south of Borno had been liberated, while six areas were still being occupied by the Islamists.

Boko Haram has also been chased out of Gujba and Gulani in northeast Yobe state, he added.