The remains of 30 migrants who died crossing the Sahara have been found in Niger, the International Organization for Migration said Tuesday, adding to a grim death toll among people seeking a new life in Europe.

On Sunday, the IOM had reported the discovery of another 18 migrants who became lost during a sandstorm in the harsh desert of northern Niger and probably died of thirst.

The bodies of 18 mainly west African migrants trying to reach Europe have been found in Niger in the Sahara desert, the International Organization for Migration said.

The 17 men and one woman are believed to have lost their way in a sandstorm after setting off from the desert town of Arlit, IOM said Sunday.

Al-Qaida-linked jihadist Mokhtar Belmokhtar, who allegedly masterminded the siege of an Algerian gas plant in which 38 hostages died, has been killed in a U.S. air strike, Libya's internationally recognized government said.

"American jets conducted an operation which resulted in the deaths of Mokhtar Belmokhtar and a group of Libyans belonging to a terrorist organization in eastern Libya," said a statement posted on Facebook.

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.