Thirty-three people were killed in Offa, including nine policemen, when six banks were targeted.

Police spokesperson Jimoh Moshood said Mr Saraki has been invited for questioning after arrested suspects said that the senate president and the state's governor had sponsored them.

They had given them firearms, money and operational vehicles, This Day newspaper reports.

“The five gang leaders… confessed and volunteered statements that they were political thugs of … Bukola Saraki and the executive governor of Kwara state Abdulfatah Ahmed.”

It is not clear when Mr Saraki will come in for questioning. He has denied having links with the suspects, saying it is a campaign to smear his image.

Mr Ahmed has denied the accusations, The Vanguard newspaper reports.