The family alleges that the men were kept in the police station all night and tortured.
The death of a father and son in police custody in Tamil Nadu's Tuticorin following allegations of torture is snowballing into a major political row and has triggered calls for law enforcement reform.
The opposition DMK targeted the state's AIADMK government over the incident, accusing it of allowing policemen to take "law into their own hands" and announced it would give Rs 25 lakh to the family of the two men.
"The alleged brutal assault on the two men days ago by police was a result of the AIADMK government allowing them to take law into their own hands at a time when they have to ensure the safety of the public during the lockdown," DMK president MK Stalin said in a statement.
P Jayaraj and his son Beniks were arrested for keeping their mobile phone shop in Tuticorin open beyond permitted hours last Friday and died at a hospital four days later. The relatives alleged that they were severely thrashed at the Sathankulam police station by police personnel.
They allege that there were injuries to the rectum and other tell-tale signs of torture on the two bodies like tufts of hair pulled from the chest, and demanded murder charges against the policemen involved. The two men had been charged with criminal intimidation and verbally abusing the cops.
Though the First Information Report (FIR) mentions the name of the son as Pennis, his family says his name is Beniks. A Madras High Court document has spelt it as Bennicks.
The incident triggered massive outrage in Tuticorin where 13 people were killed in police firing two years ago during demonstrations against a copper smelter. Shops were closed in the district and other parts of the state in protest on Friday.
Four policemen, including two sub-inspectors have been suspended and an inspector has been benched by the state government. Chief Minister EK Palaniswami, who controls the police department, condoled the deaths but was silent on the alleged torture. He has announced a total of Rs 20 lakh as compensation and a job for the family. The case has been taken up by the Madurai bench of the Madras High Court.
MK Stalin, Leader of the Opposition in the state assembly, said all those responsible for the "barbarity" should get tough punishment and his party would support all legal action for it. DMK MP Kanimozhi has also written to the National Human Rights Commission (NHRC) over the incident.
Congress leader Rahul Gandhi also spoke out about the incident on Friday, condoling the deaths and said it was a tragedy when protectors "turn into oppressors".
"Police brutality is a terrible crime. It's a tragedy when our protectors turn into oppressors. I offer my condolences to the family of the victims and appeal to the government to ensure justice for Jeyaraj and Fenix (sic)," he tweeted.
Relatives of two traders had finally accepted the bodies on Thursday, expressing hope they would get justice and following assurances given by the officials.