DMK president M Karunanidhi is facing a "slight decline" in his health, a hospital bulletin said, even as the party is gearing up for celebrating his 50th year as party chief on Friday.

"There has been a slight decline in the health of DMK president M Karunanidhi due to age related ailments," a bulletin issued by Kauvery Hospital Executive Director Dr Aravindan Selvaraj said.

The 94-year-old leader is currently being treated for fever due to urinary tract infection with intravenous antibiotics and fluids.

"He is being monitored and treated round the clock by a team of medical and nursing professionals, who are providing hospital level care at his (Gopalapuram) home," the bulletin said.

The hospital said considering his medical condition, the team has strongly advised restriction of visitors.

Earlier, in a letter to party workers, Karunanidhi's son and DMK working president M K Stalin said, "Let us celebrate the golden jubilee of our leader assuming office as party chief."

"Our beloved" leader shouldered the responsibility of heading the party as its president on July 27, 1969 after the death of DMK founder-leader C N Annadurai, Stalin said.

Hailing Karunanidhi for his 'tireless' work in steering the party for half a century, he listed the welfare initiatives launched by his father during his five terms as chief minister.

Karunanidhi worked "without any respite" all his life, Stalin said, adding that "time has given some rest," a reference to his age-related health issues.

The party was confident that "time and medical science," will fulfil the party workers' yearning to hear his 'magnetic' voice again, he said.

DMK will celebrate the event by distributing sweets and distributing welfare assistance, a party leader here said.

Karunanidhi has been not keeping well since October 2016 and days ago he had underwent a procedure to change his tracheostomy tube, provided to help breathing.

On Wednesday, Stalin had said Karunanidhi was suffering from fever and doctors were providing medication as he assured there was nothing to worry about his health.