The DMK, meanwhile, released a photograph, the first after Karunanidhi's hospitalisation early on Saturday, showing Naidu standing beside the 94-year-old leader in his hospital bed.
Party cadres outside the hospital were enthused by the release of the image.
They said the picture did not feature any "life support system like a ventilator" and it was reassuring that their Thalaivar (leader) was recuperating well.
DMK had, during the hospitalisation of late Chief Minister J Jayalalithaa in 2016, asked why no photograph of her in the hospital was released.
The party had said that release of a picture would have helped put at rest speculations about her health status.
Tamil Nadu Governor Banwarilal Purohit, DMK working president M K Stalin, party Rajya Sabha MP Kanimozhi, the nonagenarian leader's wife Rajathi Ammal and Karunanidhi's personal physician Dr Gopal are also seen in the picture.
Naidu said doctors informed him that Karunanidhi's condition was stable.
"Visited Kaveri Hospital and met former Chief Minister Thiru Kalaignar Karunanidhi. Met his family members and doctors and enquired about his health. Doctors said he is stable. Wish him a speedy recovery," Naidu tweeted.
Last night, the hospital had said, "Karunanidhi's health condition continues to remain stable with ongoing active medical support. He is continuously being monitored and treated by the panel of expert doctors in the ICU."
The 94-year-old DMK president, who is being treated for fever due to urinary tract infection, was admitted to the Intensive Care Unit (ICU) of Kauvery Hospital following a dip in his blood pressure.
Besides Naidu, CPI(M) General Secretary Sitaram Yechury, TMC leader Derek O'Brien, BJP leader Muralidhar Rao and the party's Tamil Nadu unit party president Tamilisai Soundararajan visited the hospital.
"I came here on behalf of the TMC and Mamata Banerjee. I met M K Stalin and Kanimozhi and inquired about Karunanidhi's health," the TMC leader said.
Other than Naidu and Purohit, all other leaders met Karunanidhi's family members in the hospital and enquired about his health.
All of them lauded the nonagenarian leader and wished him a speedy recovery.
Students of Tiruvarur based V S Boys Higher Secondary School, where Karunanidhi had studied, held an inter-faith prayer yesterday for the recovery of their alumnus.
Karunanidhi hails from Thirukkuvalai (Nagapattinam District) near the Cauvery delta town of Tiruvarur.