Cameroon's army says it has killed 86 Boko Haram militants and detained 1,000 people suspected of links to the Islamist group, as central African leaders held talks on how to combat its bloody insurgency.

Five Cameroonian soldiers were also killed during the clashes in the Waza region near the border with Nigeria, defense ministry spokesman Didier Badjeck said Monday.

Boko Haram invaded the restive northeastern Nigerian city of Gombe on Saturday and warned residents against voting in next month's elections as the Islamists defied regional force aiming to pursue them.

Residents said the attackers later left the city and stormed another area some 40 kilometers (25 miles) away, where they burned homes.

Nigeria-based Boko Haram Islamists carried out their first attack Friday inside Chad, killing five people in a strike on a village on the shores of Lake Chad, a security source said.

Chadian military spokesman Azem Bermandoa Agouna also confirmed the pre-dawn attack on Ngouboua, a village across the water from the Nigerian town of Baga.

Chad's President Idriss Deby has taken up the fight against Boko Haram at the risk of offending diplomatic sensibilities in Africa, but to the delight of his international allies.

One Western diplomat described Deby, who seized power in 1990, as "first and foremost a fighter," who for years had battled rebels intent on ousting him from power, while at the same time arming those fighting the authorities in neighboring Sudan.

Boko Haram on Wednesday launched a pre-dawn raid in Gamboru, northeastern Nigeria, looking to overwhelm Chadian troops who had pushed them out of the border town.

The military in N'Djamena said the militants were repelled but the counter-attack was an indication of the task facing regional forces aiming to crush the rebellion.

Niger is set to send troops to Nigeria for the multi-national battle against Boko Haram after scores of people were killed in a fresh onslaught by the Islamist fighters in a key border town.

Intervention from Niger would open a new northern front in the increasingly regional fight against the Islamist insurgents who killed more than a hundred people, including 19 soldiers, on Wednesday in a rampage in the Cameroonian town of Fotokol on Nigeria's border.

Niger is set to send troops to Nigeria for the multi-national battle against Boko Haram after scores of people were killed in a fresh onslaught by the Islamist fighters in a key border town.

Intervention from Niger would open a new northern front in the increasingly regional fight against the Islamist insurgents who killed over a hundred people, including 19 soldiers, on Wednesday in a rampage in the Cameroonian town of Fotokol on Nigeria's border.

French investigators were Wednesday interrogating a knife-wielding man who attacked three soldiers outside a Jewish center in Nice, as questions resurfaced over security measures a month after the Paris attacks.

The attacker, identified as 30-year-old Moussa Coulibaly from the poor western suburbs of Paris, was already known to police who questioned him just days before the attack, when he was turned away from Turkey last week.

Nigerian Boko Haram fighters went on the rampage in the Cameroonian border town of Fotokol Wednesday, massacring civilians and torching a mosque before being repelled by regional forces.

The onslaught came a day after Chad sent troops across the border to flush the jihadists out of the Nigerian town of Gamboru, which lies some 500 meters (yards) from Fotokol on the other side of a bridge.

Chadian forces scored a key victory over Nigeria's Boko Haram on Tuesday, wresting control of the border town of Gamboru within hours of launching a ground offensive against the jihadist group.

Around 2,000 Chadian troops backed by armored vehicles crossed the border into Gamboru from the Cameroonian town of Fotokol after days of clashes with the insurgents.