The west African country of Niger, where there are tens of thousands of modern-day slaves according to unofficial estimates, on Friday became the first country to sign a U.N. protocol to stamp out the practice.

"This is a historic moment -- by being the first country to ratify the protocol, Niger has ensured that the protocol is well on the way to entering into force," Guy Ryder, the head of the International Labor Organization said at a ceremony in Geneva. 

Niger's President Mahamadou Issoufou, facing a fragmented opposition, has said he wants to ensure next year's presidential and parliamentary elections are "transparent".

Issoufou's statement to public television on Wednesday evening came after launching a new voter registration process.

Nigeria's new president, Muhammadu Buhari, on Wednesday promised to look into an Amnesty International report urging the International Criminal Court to probe senior military officers for war crimes in the battle against Boko Haram.

"I assure you that your report will be looked into," an official statement quoted Buhari as saying in Niger's capital Niamey, in his first reaction to the group's 133-page report.

Nigerian President Muhammadu Buhari said during a visit to Niger's capital Wednesday that he was seeking help from neighboring countries to eradicate the Islamist group Boko Haram before they do "more serious damage."

"I'm coming to seek the support of our neighbors. I came first to Niger, tomorrow I will go to N'Djamena and I will also talk with the president of Cameroon, to seek out ways and means to reinforce our efforts," said the recently-elected president during his first official trip abroad. 

A soldier in fatigues furiously pedals his bicycle through the alleyways of Diffa, puffing away after the biggest town in southeast Niger banned motorcycles -- vehicle of choice of jihadists.

Situated on the border with northeastern Nigeria, the heartland of Boko Haram insurgents, Diffa is on high alert since it was attacked in February.

Nigeria's new President Muhammadu Buhari will this week make his first foreign trip since taking office, traveling to Chad and Niger for talks on Boko Haram, his spokesman said on Monday. 

Shehu Garba said the two-day trip starting on Wednesday will focus on "matters of security", with the cooperation of Nigeria's neighbors seen as crucial to ending the Islamist uprising which has claimed more than 15,000 lives since 2009. 

Nigeria's military on Saturday repelled a Boko Haram attack on the key northeastern city of Maiduguri, a day after President Muhammadu Buhari took office vowing to crush the group, witnesses and security sources said.

The overnight attack on the Borno state capital saw rocket-propelled grenades fired into homes in a bombardment that reportedly lasted several hours.

A clash between Chad's army and Boko Haram on a Lake Chad island has killed four soldiers and 33 Islamists, a military spokesman said Friday.

"Boko Haram elements on Wednesday attacked our forces in Choua," military spokesman Colonel Azem Bermandoa Agouna told AFP, referring to a Lake Chad island in Chadian territory.

A fundraising campaign to help Cameroon's army battle Nigeria's feared Boko Haram fighters has brought in more than three million euros and hundreds of tonnes of food, local media said Wednesday.

"2.1 billion CFA francs (3.2 million euros) already" collected to help troops fighting the Islamist group on Cameroon's northern border with Nigeria, said the national CRTV radio and TV network.

Niger has extended for three months the state of emergency in its southeastern Diffa region where the army has been battling Boko Haram militants since February, authorities announced Wednesday.

"Boko Haram elements are there," Daouda Malam Marthe, first vice president of parliament, said on state radio. "The prolongation of the state of emergency is a necessity."