The police said the detained people have no previous crime records against them.
The plan to execute former Hindu Mahasabha President Kamlesh Tiwari was made about two months ago by the detained accused over the hate speech given by him, officials said today.
The revelations were made a day after Mr Tiwari was murdered by two people, who came to his Lucknow office in Khurshid Bagh area wearing saffron kurtas and with a box of sweets with an address of a Surat sweet shop on Friday afternoon. The men had kept the pistol and the knife in the sweet box.
Gujarat Anti-Terror Squad (ATS) DIG Himanshu Shukla told news agency IANS: "The three people, whom we detained in the morning have confessed to their crime of killing Tiwari."
Mr Shukla said that the plan to execute Mr Tiwari was made about "two months" ago as these people were offended over the provocative statements made by him.
The three people detained by the joint team of Gujarat Police, Gujarat ATS and the UP Police have been identified as Maulana Mohsin Sheikh, Faizan and Khurshid Ahmed Pathan.
The ATS officer also said that the three people who have been detained by the police have no previous crime records against them.
Earlier in the day, Uttar Pradesh Police Director General of Police (DGP) OP Singh informed about the detention of three people from Surat in connection with the murder of Tiwari.
He said, "Khurshid Ahmed Pathan was the mastermind behind Kamlesh Tiwari's murder."
Singh also said that the police initially detained five people from Surat, but two were released later. "Their activities are being monitored," said Mr Singh.