Nigeria's military on Wednesday claimed for the first time that Boko Haram leader Abubakar Shekau was dead, as it said troops had killed a lookalike who had been posing as the militant commander.

Defence spokesman Chris Olukolade told reporters in Abuja that a heavily bearded Islamist fighter identified as Mohammed Bashir died during fighting in the town of Konduga, in Borno state.

Gunmen kidnapped a Chinese national from his residence in central Nigeria's Kogi state, police said on Wednesday, vowing to track down the attackers and free the hostage.

"The incident happened in the early hours of Tuesday when armed men stormed the official residential quarters of the Kogi State Water Corporation and abducted a Chinese national," police spokesman Elvis Aguebor told Agence France-Presse.

Nigerian officials were tight-lipped on Tuesday about the scope of a probe into a fatal church building collapse in Lagos that killed 115, as anger mounted against the popular preacher in charge.

The Lagos state governor's spokesman, Hakeem Bello, said the government in Abuja had convened a committee of state and federal agencies to investigate the September 12 collapse.

Is he alive or isn't he? Fresh claims have emerged in Nigeria that Boko Haram leader Abubakar Shekau, or at least someone impersonating him, may be dead -- and not for the first time

Rumours have been flying since last Thursday when the military tweeted that "a seriously wounded high ranking terrorist leader" had been captured during clashes in Konduga, Borno state, in the country's strife-torn northeast.

The death toll from the Nigerian church collapse has now climbed to 115 people, with 84 of them South Africans, a South African minister said Monday, citing sources in Lagos.

"We understand from our assessment team that the total number of people who have perished is now 115, but those are not all South Africans," said Jeff Radebe, the minister in charge of Pretoria's response to the disaster.

Nigerian President Goodluck Jonathan on Saturday visited the collapsed guesthouse at a mega-church in Lagos, promising to investigate the cause of the tragedy as the death toll hit 86, rescuers said Saturday.

"The president came to the church this morning to see things for himself. He met with Prophet T.B. Joshua and expressed his condolences to the bereaved families," Ibrahim Farinloye of the National Emergency Management Agency told AFP.

Nigerian presidential hopeful Atiku Abubakar on Friday derided Goodluck Jonathan's record on security, vowing that Boko Haram could be crushed easily if politicians chose to do so.

Abubakar, who was vice president under Olusegun Obasanjo from 1999 to 2007, is looking to win the presidential ticket for the main opposition All Progressives Congress (APC) at next year's vote.

The number of South Africans known to have died in the collapse of a multi-storey megachurch in Lagos last week has risen to 84, Pretoria's high commissioner to Nigeria said Friday.

Boko Haram militants are in charge of at least 25 towns and villages in northeast Nigeria, the region's Roman Catholic bishop has claimed, warning of a deteriorating security situation.

Bishop Oliver Dashe said 10 towns in Yobe state, the same number in Borno and five in Adawama had fallen to the rebels over the last month, as they seek to carve out a hardline Islamic state.

Amnesty International on Thursday urged Nigeria's government to criminalise torture, as it published a new report documenting widespread abuses in the criminal justice system and military.