A Nigerian human rights group on Monday asked the International Criminal Court to bring charges against Nigerian presidential candidate Muhammadu Buhari for post-election violence in 2011.
The Northern Coalition for Democracy and Justice said in a statement Buhari should face justice over the violence, when 800 people were killed and many churches and schools were destroyed.
The ICC has been looking into possible war crimes in Nigeria since 2010, but few believe it would be keen to take on another powerful politician after being forced to drop charges against Kenyan President Uhuru Kenyatta earlier this month.
Buhari's All Progressives Congress party denied the claims, saying they were politically motivated. "They will not stop at anything to try to derail General Buhari," said spokesman Lai Mohammed. "I can see the hands of the government behind it."
Nigerian officials were not immediately available to respond.
The court's prosecutor receives dozens of such submissions each year, of which very few ever result in investigations.
The NCDJ alleged the violence included acts of murder, torture and rape systematically directed at perceived non-supporters of Buhari.
The NCDJ had previously referred Buhari to the ICC in 2011, but said it decided to submit more evidence after the former military ruler emerged as the main candidate in February's presidential elections.
"We have a lot of very strong evidence we are submitting to the prosecutor," said Goran Sluiter, a Dutch law professor acting for the NCDJ, adding he wanted to ensure Buhari did not escape justice by winning political office.
Earlier this month, the ICC withdrew charges against Kenyatta, who was accused of orchestrating a wave of deadly violence after the 2007 Kenyan elections, due to insufficient evidence.
Observers say the ICC charges were a key factor in helping Kenyatta secure the presidency two years ago, from which position he was able to lead Kenya and its African allies in a campaign of lobbying against the court's charges.
Buhari, 71, has been an influential political figure in Nigeria for much of its post-independence history, leading a military government for two years until 1985.
The ICC was set up 12 years ago to try those suspected of serious international crimes in cases where local authorities are unable to do so. It has been criticized for bringing weak cases and securing just three convictions.