The Anti-Terrorism Squad of the Maharashtra police on Saturday arrested a man in connection with the murder of Kamlesh Tiwari, the leader of a political party in Uttar Pradesh, an official said.
The ATS official said the arrest was made on the basis of leads provided by the UP Police.
The arrested man has been identified as 29-year-old Sayed Asim Ali. Officials said he runs a hardware business in the city.
Sayed Ali had organised a protest against Kamlesh Tiwari in the past and also issued threats to him in a YouTube video, the police said.
Kamlesh Tiwari, 45, leader of the lesser-known Hindu Samaj Party was murdered at his home in Lucknow on Friday.
Earlier on Saturday, UP police had arrested five suspects in the case.
The suspects were "radicalised" and appeared to have targeted Kamlesh Tiwari for his inflammatory remarks made in 2015, the police said.