Tamil Nadu ministers O Panneerselvam, others met Karunanidhi's son MK Stalin.
Tamil Nadu politicians including deputy chief minister O Panneerselvam and actor-politician Kamal Haasan called on the ailing DMK chief Karunanidhi late on Thursday evening after what doctors described as a "slight decline" in his health.
Mr Karunanidhi, 94, is being treated at his Gopalapuram residence by a team of doctors, a health bulletin issued by Kauvery Hospital Executive Director Dr Aravindan Selvaraj said.
The bulletin said there was a "slight decline" in Mr Karunanidhi's health and he is being treated for fever due to urinary tract infection with intravenous antibiotics and fluids.
Mr Karunanidhi, who has served as Tamil Nadu Chief Minister five times, has been recovering from a long illness for more than a year and is rarely seen in public.
Son, MK Stalin, 65, serves as working president of the party founded by his father's mentor CN Annadurai, in 1949 and daughter Kanimozhi, a Rajya Sabha Member of Parliament, also looks after party affairs.
The DMK patriarch had returned home recently after a short stay at hospital where he underwent a procedure to change his tracheostomy tube to help him breathe better. Dr Selvaraj said he is being provided hospital level care at home and strongly advised the family to restrict visitors.
As word about the decline in his health spread on Thursday night, political leaders - friends and rivals alike - reached his house.
The ruling AIADMK's O Panneerselvam and fisheries minister D Jayakumar were among the first to reach his residence. In photographs that emerged, the deputy chief minister and his cabinet colleague are seen sitting in a room with MK Stalin and other senior DMK leaders.
Kamal Haasan, who had received an offer from Mr Karunanidhi to join politics back in 1993, also was there to inquire about the veteran politician's health. So were Thirumavalavan of the Viduthalai Chiruthaigal Katchi and former union minister GK Vasan, who broke away from the Congress to revive the Tamil Manila Congress two years ago.
On his way out, Mr Panneerselvam and his cabinet colleague D Jayakumar told reporters that Mr Karunanidhi was "doing well."
"Mr Karunanidhi will return in good health soon," Mr Jayakumar said.
Mr Jayakumar said it was political decency for the ruling party to visit the opposition leader's residence, recalling that a DMK delegation had extended a similar courtesy to AIADMK matriarch J Jayalalithaa when she was undergoing treatment at hospital in 2016.