Boko Haram are no longer in a position to seize a single town in Niger, a Niger government minister said on Saturday, following a regional effort to boost the fight against the Islamist group.

Thousands of troops from Niger and Chad, which had gathered in southeastern Niger, launched a major ground and air offensive against the Islamist group last Sunday and succeeded in retaking the northeastern Nigerian town of Damasak.

Troops from Chad and Niger have retaken the northeastern Nigerian town of Damasak from Boko Haram as part of a regional offensive to combat the militants who have pledged allegiance to the Islamic State group.

Boko Haram had held the town near the Niger border since November, part of a swathe of territory it had seized in Nigeria's northeast, where the group's six-year insurgency has been based.

The armies of Niger and Chad on Sunday launched a major ground and air strike against Boko Haram in northeastern Nigeria, opening a new front in regional efforts to eradicate the Islamist militants. 

The offensive announced by a source in the Niger government came after Boko Haram leader Abubakar Shekau pledged allegiance to the Islamic State group in an audio message.

The African Union has endorsed the creation of a regional force of up to 10,000 men to join the fight against the Nigerian Islamist group Boko Haram, diplomats said Friday.

The force, the idea for which was adopted at an AU summit in January, will be based in Chad's capital N'Djamena, the pan-African bloc's Peace and Security Council said.

At least 19 civilians were killed in a weekend attack by Boko Haram Islamists on three remote islands in Niger with many victims burnt alive, a local lawmaker said.

Sunday's onslaught took place on three islands located on Lake Chad, said ElHadj Aboubacar, a deputy from the town of Bosso in southeastern Niger.

Bomb attacks in Nigerian towns and cities look likely to increase in the run-up to forthcoming elections, despite the military claiming increasing successes against Boko Haram in captured territory.

At least 86 people were killed in explosions blamed on Boko Haram this week alone, all of them at crowded bus stations in the northeast, wider north and also in the country's central region.

Aboubacar, usually a worker for a non-governmental organisation, has now taken on another, more ominous role: watching out for suicide bombers.

"We watch everyone," he said in Niger's second-largest city of Zinder. "Last Thursday, a man in a turban whom we had never seen before came to the mosque. We asked him to leave."

At least 36 mourners at a funeral ceremony were killed and 27 wounded when an unidentified plane bombarded a village in Niger near the Nigerian border, the army said Wednesday.

The strike on Tuesday came as Niger takes part in a regional offensive against Nigeria-based Boko Haram fighters, who have extended their brutal six-year insurgency to Niger, Chad and Cameroon.

Four African armies, from Nigeria, Cameroon, Chad and Niger, are currently directly engaged in the fight against the Nigeria-based insurgent group Boko Haram.

Regional forces have gone into action while awaiting the formation of a planned 8,700-strong, five-country force, whose make-up remains to be determined.

Hundreds of Boko Haram militants stormed the town of Askira Uba in northeast Nigeria, burning homes and public buildings, as attacks continued despite a regional campaign against the Islamist rebels, witnesses said Tuesday.

Residents able to flee the town in Borno state left in droves, with only the sick and elderly remaining behind through the insurgents' rampage.