Two suicide bombers killed a soldier at a checkpoint in Boko Haram's heartland in northeastern Nigeria, vigilantes helping troops in the fight against the jihadists told AFP on Wednesday.

The militants, a man and a woman, were in a motorized rickshaw stopped by a soldier on the outskirts of Borno state capital Maiduguri around 10:30 pm (2130 GMT) on Tuesday, an hour into the area's night-time curfew.

Relatives of more than 200 Nigerian schoolgirls kidnapped by Boko Haram said they would hold a youth march and candle-lit vigil on Thursday to mark 500 days since the abductions.

Boko Haram fighters stormed the Government Secondary School in the remote town of Chibok in Borno state on April 14 last year, seizing 276 girls who were preparing for end-of-year exams.

French President Francois Hollande offered Tuesday to organize an international meeting on tackling jihadist group Boko Haram that has killed thousands in Nigeria.

"In several days, I will receive the new Nigerian President (Muhammadu) Buhari and I will confirm to him that France is ready to unite all the actors in the fight against Boko Haram," Hollande said during a speech to diplomats on Tuesday.

A child bomber killed six people and wounded dozens on Tuesday outside a bus station in the heartland of the Boko Haram Islamist insurgency in northeastern Nigeria.

Witnesses reported seeing a "young girl" approaching the station in the Yobe state capital Damaturu around 7:00am (0600 GMT) and refusing to be searched by security guards at the gate before blowing herself up.

U.N. chief Ban Ki-moon on Monday hailed Nigeria's "greater stability and peace" under its new leader as he commemorated a deadly attack on the global body by Boko Haram militants.

The secretary-general hugged relatives of the victims of the 2011 bombing as he laid a wreath at United Nations House in the capital Abuja and praised "the extraordinary fortitude and determination" of the survivors.

Nigeria's President Muhammadu Buhari suspended his head of immigration Friday, the government announced, with the department under investigation over the approval of a visa to Islamist Lebanese cleric Ahmed al-Asir.

Asir, wanted in Lebanon over deadly clashes with the army and other cases, was arrested on Saturday at Beirut's airport as he tried to board a plane to Nigeria using a fake Palestinian passport with a valid visa.

Two Nigerian soldiers died during an advance through Boko Haram's northeastern stronghold on Friday when they stepped on a land mine buried by the Islamists, the army said.

Two other troops were seriously wounded in the explosion in Dikwa, a town in Borno State that was recaptured from the jihadist group in July, army spokesman Sani Usman said in a statement.

U.N. chief Ban Ki-moon is to visit Nigeria to commemorate a deadly attack on the global body by Boko Haram militants and meet the country's new leader, the government said Friday.

The secretary-general arrives in Abuja on Sunday, where he will have talks with President Muhammadu Buhari, who came to power on May 29, and lay a wreath to commemorate the fourth anniversary of the attack.

The number of villagers massacred by Boko Haram jihadists in a remote village in northeastern Nigeria rose to 160 on Wednesday, according to locals, as the military rejected accounts of the attack.

Residents of Kukuwa-Gari in Yobe State described how more than 150 of their relatives and neighbors drowned in a river fleeing militants who opened fire on the village on Thursday last week, while another eight were shot dead.

Up to 150 people drowned in a river or were shot dead fleeing Boko Haram gunmen who raided a remote village in Nigeria's northeastern Yobe state, local residents said on Tuesday.

Dozens of militants arrived on motorcycles and in a car on Thursday last week and opened fire, scattering terrified residents of Kukuwa-Gari.