Kauvery hospital had said yesterday evening that Karunanidhi's condition had "declined" and keeping his vital organs functioning remained a "challenge".
Karunanidhi was admitted to Kauvery hospital in Chennai following a drop in blood pressure on July 28.
DMK chief Karunanidhi is on continuous monitoring and being treated with active medical support, the hospital added.
Some reports said the government was reluctant about allotting space for Karunanidhi's burial at the Marina as he was not a sitting chief minister.
Tamil Nadu Chief Secretary Girija Vaidyanathan had said Karunanidhi will not be buried by the Anna Memorial on the beach, Puthiya Thalaimurai reported.
His last tweet was also a photo with Karunanidhi, when he went to wish him for his 94th birthday in June. Following the death of Annadurai in 1969, he took over as leader of the DMK and as chief minister, a post he would hold for almost 18 years over five separate terms.
Karunanidhi, who always appeared in public with dark glasses and a yellow shawl draped on a shoulder, built his career fighting oppression by Brahmins, a priestly community at the top of the Hindu caste system. Many were seen weeping and chanting slogans hailing the leader. Since then he continues to be monitored by a team of specialists, reported PTI.
Karunanidhi married thrice. His first wife was Padmavathy Ammal, with whom he had a son M K Muthu, but both of them died at young age.
The same year he parted with 50% of the seats to the Congress in the Assembly elections but the alliance was not fruitful and MGR won. The two parties have been sharing power in the state ever since.
Stalin was accompanied by some party colleagues.
Later, after Jayalalithaa's death in December 2016, he had expressed regret, saying "I had hurt her".
He introduced many social welfare measures, particularly for the poor, and played a huge role in converting Tamil Nadu into one of India's more prosperous states.