Some civil society activists backed the opposition party’s rejection of the initial results and ‘collusion’ accusations.
Nigerians have cast their vote in governorship and state assembly elections, the second poll in a fortnight, as monitors expressed concerns about political violence, vote-buying and an increased military presence.
Saturday’s election comes two weeks after Muhammadu Buhari secured a second four-year presidential term and is expected to be contentious in some areas.
The country’s two top political parties are vying for control of powerful states that – in certain cases – have budgets larger than that of some African nations.
The Situation Room, an umbrella organization of more than 70 civil society monitoring groups, warned about an “escalation of violence between and within political parties and their supporters” during Saturday’s voting.
In several states, the “partisanship of security agencies” and “an intimidating presence of military personnel,” was a concern, the group said, reporting that military fighter jets had been deployed in parts of the country.
Heavy military deployment was reported in Rivers state in Nigeria’s restive south.
Buhari will be expecting to consolidate his February 23 victory, in which he won 19 states to secure a second term in office.
His All Progressives Congress (APC) currently controls 22 states while the main opposition Peoples Democratic Party (PDP) has 13.
The All Progressives Grand Alliance (APGA) has one.
Elections were held to choose new governors in 29 of Nigeria’s 36 states, all state assemblies, and the administrative councils in the Federal Capital Territory of Abuja.
Polling stations opened at 07:00 GMT and closed at 13:00 GMT, with results expected early next week.
Local officials confirmed to The Associated Press news agency that electoral facilities in Benue and Ebonyi states had been burned. Observers note scattered reports of thuggery or suspected underage voters.
And Nigeria’s top anti-corruption agency says it has intercepted “bags of cash meant for vote-buying”.
Queues outside polling centres in the capital Abuja were shorter compared with two weeks ago when voters cast their ballots in the presidential poll.
“People are not coming out to vote because they are disappointed with the outcome of the presidential election and that has affected the turnout of today’s election,” Obinna Okeke, a businessman, told Al Jazeera.
Many of the voters said they found the voting process easier compared with previous elections.
“It was easy to vote today. People are not many today as compared to the previous elections. The card reader worked smoothly when I was getting accredited,” Edidiong Bassey, a 35-year-old civil servant, told Al Jazeera.
Governors are powerful and influential figures in Nigeria’s federal politics, controlling state finances, and controlling key areas including education to health.
With so much at stake, many previous governorship elections have been marred by violence, including shootings and armed gangs snatching ballot boxes.
Buhari beat Atiku Abubakar of the People’s Democratic Party (PDP) in last month’s presidential election with 15.2 million votes to 11.3 million, although turnout was just 35.6 percent.
State-level elections are often predicted to broadly mirror presidential polling and this year comes amid concerns about the role of security forces during the vote.
During the presidential and parliamentary polling, there were reports of violence, vote-buying, voter intimidation and ballot box vandalism in some states.
At least 53 people have been killed, according to the Situation Room, which said safety fears contributed to a low turnout.