More than 300 people were arrested on suspicion of electoral fraud during the last Nigerian elections, the chief police chief said.
"So far, 323 offenders have been arrested across the country for various electoral crimes and various crimes," said Police Inspector General Mohammed Adamu on Monday.
"Two officers also paid the highest casualty while others were attacked and injured," he added, vowing to contact the electoral commission for a possible persecution.
In the February 23 poll, incumbent President Muhammadu Buhari of the All Progressives Congress was defeated by his main rival, Atiku Abubakar of the People's Democratic Party.
Abubakar denied the result, described the election as a "slip" and promised to file a lawsuit.
Nigeria, the most populous nation in Africa, has used electoral violence and malpractice in the past, including electoral cuts, intimidation of voters and ballots.
In the poll, which Buhari won with nearly four million votes, 53 people were killed and scores of others injured, according to surveillance groups.
In 2011, more than 1 000 people were killed after the elections in northern Nigeria.