The National Investigation Agency (NIA) Friday arrested a 48-year-old man from Tamil Nadu's Trichy city in connection with the Ramalingam murder case.
Mohammed Faruk was arrested a day after the NIA officials conducted a search operation at his residence in Illangakurichy village in Tiruchirappalli district during which they seized some digital evidence, officials said.
He was summoned for questioning by the officials on Thursday.
The evidence collected from the residence and his questioning revealed the extent of involvement of Faruk in the case, the officials said.
Ramalingam was attacked by a gang on February 5. The accused used sickles and tried to chop off his hands, grievously injuring him in the process.
His son's efforts to protect him from the attackers were in vain. He was pronounced dead at a government hospital on February 6.
Faruk and other accused had hatched a criminal conspiracy for committing a terrorist act pursuant to which they chopped off the hands of Ramalingam, the officials said.
The Tamil Nadu Police has arrested 10 accused in the case. Six others are still absconding.
Faruk will be produced before the Special NIA Court, Poonamllee in Chennai, on Saturday.
Ramalingam, 42, was murdered when he was on his way to home at Muslim Street in Thirubuvanam. He was murdered the same day he confronted a few men who attempted to convert people to Islam.
Ramalingam removed the skullcap worn by one of the men in the gang and put ash on his forehead.
Initially, a case was registered at Thiruvidaimarudur police station in Thanjavur district on February 6. Later, the case was taken over by the NIA.
On May 2, the NIA conducted searches at 20 places in Kumbakonam, Trichy and Karaikkal and seized incriminating materials, the officials said.