Nigeria's Independent National Electoral Commission (INEC) announced it would conduct fresh polls in areas where violence marred the presidential and national assembly elections held on Saturday.
The election were conducted after being postponed for a week following what INEC said were logistical challenges.
The country was generally peaceful on Sunday as citizens patiently assessed the allegations of rigging by the two major parties, the ruling All Progressives Congress (APC) and the opposition Peoples Democratic Party (PDP).
President Muhammadu Buhari, the candidate of APC was still in his Daura Village in Katsina State where he cast his vote while his main challenger, former Vice-President Atiku Abubakar of PDP, was in Yola in Adamawa where he also voted.
The social media was, however, agog with unofficial results.
Voting in Abuja metropolis was peaceful except in one area in Maitama where already thumb printed and stuffed ballots were intercepted by voters who alerted the security agencies.
Early results collated at polling units, though unofficial, indicated that Senate President Bukola Saraki from Kogi may not be returning to the senate as he had been defeated by Dr Ibrahim Oloriegbe of APC.
The results announced at the polling units, would be officially announced by INEC.
The two main presidential contenders, President Buhari, 76 and Mr Abubakar, 72, belong to the same ethnic nationality and are both Muslims, in a country where religious and regional considerations have traditionally defined the voting patterns.
Until months to the election, Mr Abubakar, an ex-customs service officer, was in the same party with President Buhari from PDP where he had served as vice-president under Olusegun Obasanjo.
Mr Abubakar lost the 2014 APC presidential primary to President Buhari and later decided to return to PDP.
To win the presidency in the first round, a candidate must garner a majority of the vote and over 25 per cent of the ballots in at least 24 of the 36 states. If no candidate passes that threshold, a second round is held.