Padamsinh Patil, a Nationalist Congress Party (NCP) MP and a former Maharashtra home minister, was arrested by the Central Bureau of Investigation (CBI) late on Saturday night in connection with the murder of a Congress leader in 2006, official sources said in Mumbai.
Patil, who represents Osmanabad in the Lok Sabha, was earlier detained after being questioned till late into the night, the sources said.
He is likely to be produced before a court in Panvel on Sunday, the sources added.
Congress leader Pavan Raje Nimbalkar, who was Patil's cousin, was shot dead by two gunmen at Kalamboli near Mumbai on July 3, 2006 after he was lured there under the pretext of striking a business deal.
The CBI had last week arrested two people who have been charged with Nimbalkar's killing. The duo have revealed that they had also been given a contract to kill Magsaysay Award winner and social activist Anna Hazare.