A Dutch lawyer at the ICC and Nigerian rights activists say they have evidence showing Nigeria's 2015 presidential candidate Muhammadu Buhari instigated violence that led to the killings of some 800 people after he lost 2011 elections.

"There are references to lynching, there's a reference to killing," lawyer Goran Sluiter says of video recordings of the former military dictator.

Activist Yunana Shibkau says they will use such recordings to convince the International Criminal Court to charge the retired general with crimes against humanity.

They spoke to The Associated Press before a news conference Thursday in Abuja, saying they hope to pre-empt similar violence next month.

Buhari's campaign has said such allegations are political gimmicks orchestrated by President Goodluck Jonathan, Buhari's chief rival. Buhari ousted a democratically elected president in 1983.