Chennai, Dec. 5: Tamil Nadu chief minister Jayalalithaa died on Monday night after a day of suspense and political drama in Chennai, losing her 75-day battle with severe illness that culminated in a cardiac arrest on Sunday evening. She was 68.

Her finance minister O. Panneerselvam was sworn in as chief minister around 1.15am on Tuesday.

Jayalalithaa had been admitted to Apollo Hospitals here on September 22 with fever and dehydration but soon developed septicaemia or blood poisoning, which affected her lungs and heart.

She had earlier been on ventilator for several days. After the cardiac arrest, she was put on an ECMO apparatus, used for oxygenating and circulating the blood in patients whose heart and lungs are failing.

At 12.16am on Tuesday, Apollo Hospitals officially announced she had died at 11.30pm on Monday. It said every possible clinical attempt had been made to resuscitate her.

"However, despite our best efforts the honourable chief minister's underlying conditions rendered her unable to recover and she passed away at 11.30pm today (5.12.2016)," the bulletin said.

Earlier in the evening, a false call by some local television channels had caused much confusion. Their announcement of Jayalalithaa's death around 5.30pm had led anguished cadres to lower the party flag at the AIADMK headquarters to half mast, only to raise it again after Apollo dismissed the reports.

But everyone realised it was only a matter of time. Apollo prepared the public for the final call by releasing several bulletins during the day that clearly pointed to Jayalalithaa's deteriorating health.

The first bulletin said she was "seriously" critical. Then the hospital's deputy director posted a tweet describing her "situation" as "grave".

Finally, the hospital quoted Dr Richard Beale, the London specialist treating her, as saying "the situation is extremely grave".

Dr Beale admitted that Jayalalithaa always ran the risk of further medical complications in spite of the progress she had made.

Politically, the day was packed with drama. First, Jayalalithaa's friend Sasikala tried to derail Panneerselvam, the consensus successor among the MLAs, by suggesting the candidature of Lok Sabha deputy Speaker M. Thambidurai.

The MLAs quickly shot this down as Panneerselvam had twice before been Amma's choice as her replacement when the courts had briefly unseated her.

Later, as the cadres prepared for the worst, the party whip called a meeting of MLAs at the AIADMK headquarters at 6pm. But senior ministers stayed put at Apollo, waiting for a signal from Sasikala.

There were allegations that Sasikala wanted more time to muscle her way in as the chief ministerial candidate at the MLAs' meeting.

But a Union minister reportedly signalled that the Centre was behind Panneerselvam since it did not want any political instability arising from Sasikala succeeding Jayalalithaa.

Around 11pm, Panneerselvam and other senior ministers arrived at the party headquarters and the meeting resumed. The team of doctors from AIIMS, Delhi, and Apollo chairman Dr Pratap Reddy drove out of the hospital. Assembly Speaker Dhanapal met the governor along with senior officials.

After Apollo issued the bulletin, a sobbing Panneerselvam broke the news to the MLAs, who elected him leader of the legislature party.

Jayalalithaa's usual convoy drove into Apollo around 11.30pm to take her home to Poes Garden for the last time.

Bengal chief minister Mamata Banerjee was among the first to express her condolences. Mamata tweeted in Tamil and English: "Popular, strong, bold, efficient, people-friendly, charismatic leader, Amma. Always at the heart of people. Big loss. I am shocked, saddened. I humbly urge the people of Tamil Nadu and AIADMK to face this big loss with courage and greatness. May she rest in peace."

Sources said Mamata might go to Chennai.

Prime Minister Narendra Modi said: "Her demise has left a huge void in Indian politics."