Moments before Nigeria's Independent National Electoral Commission (Inec) was due to read out the final batch of results in a knife-edge election on 31 March 2015, a ruling party official for incumbent President Goodluck Jonathan disrupted the proceedings saying he had no confidence in the chairman.

Waving a piece of paper, an official for the People's Democratic Party (PDP), Peter Godsday Orubebe, stood in the National Collation Centre in Abuja and accused Inec of failing to address complaints on voting irregularities.

Shouting "Jega is Pacha", the former minister of Niger Delta affairs, accused chairman Professor Attahiru Jega of favouring the opposition's All Progressive Congress (APC) party and of listening only to their election complaints.

He was referring in particular to Inec's decision to send a committee to Rivers State, a Jonathan stronghold in the south, to investigate APC allegations of voting irregularities. Petitions from the APC in Rivers State were sent to the Inec chairman calling for outright cancellation of the elections in the state.

Jega said: "As I speak with you now I have not received anything from the secretary to the commission. That is with regards to the issue of the so called petition."

Police used tear gas on 30 March to disperse about 100 women dressed in black protesting against Inec in Port Harcourt, in Rivers States, saying they had been denied the right to vote.

Responding to an allegation that results had already been published on a website, he added: "With regards to what you said about results published by, allegedly published by APC on its website, I... I do not give results to anybody. The results we announce formally as Inec are results that are declared here."

Nigerian opposition contender Muhammadu Buhari, an ex-general who first won power three decades ago in a military coup, was closing in on a historic election victory, maintaining a hefty lead in the vote count in Africa's most populous nation.

According to a Reuters tally collated from 34 of Nigeria's 36 states, the 72-year-old Buhari had more than 14m votes, testament to the faith Nigerians have put in him as a born-again democrat intent on cleaning up Nigeria's corrupt politics.

Buhari's support compared to 11m for President Goodluck Jonathan, whose five years at the helm of the richest country in Africa have been plagued by corruption scandals and an insurgency by Islamist Boko Haram militants.

One of Jonathan's big support bases in the oil-producing Niger Delta is yet to report but the gap is so large that most analysts said it was impossible to see the leader of the ruling People's Democratic Party (PDP) closing it.