Chennai: Tamil Nadu Chief Minister J. Jayalalithaa is alive and on life support, Apollo Hospitals announced on Monday evening, after a TV report about her death sparked trouble and mass frenzy.

"Some TV channels are wrongly reporting that the Chief Minister is no more. This is totally baseless and false," a statement from the hospital said, denying a Sun TV report that Jayalalithaa was no more.

The hospital said Jayalalithaa, 68, who suffered a cardiac arrest on Sunday evening, "continues to be on life support at the hospital".

A large number of doctors from Apollo and AIIMS continue to provide all life saving measures, tweeted Sangita Reddy, Managing Director of Apollo Hospitals.

The clarification came after the TV channel report triggered frenzy both outside the hospital, where thousands had gathered since her cardiac arrest on Sunday evening, and at the AIADMK headquarters.

A group of emotionally charged AIADMK activists tried to barge into the hospital after breaking the barricades but were pushed back. Many others broke down, unable to check their emotions, loudly crying "Amma, Amma!"

Some people hurled water bottles at police.

At the AIADMK headquarters in Chennai, the party flag was brought down to half mast but was restored to its original position once the Apollo clarification came.

Inside, hundreds of people wept on hearing the Sun TV report. "How can you leave us?" cried one man. 

Earlier, Apollo said: "Despite our best efforts, our beloved CM remains in a grave situation."

Richard Beale from the London Bridge Hospital, who has been regularly consulted by doctors in Chennai, said the situation for Jayalalithaa was "extremely grave".

"I can confirm that everything possible is being done to give her the best chance of surviving (the cardiac arrest)," he added.

Earlier, AIADMK MLAs, apparently to pick a successor, trooped to the hospital, which has turned into a virtual fortress with hundreds of police personnel trying to keep at bay the thousands of Jayalalithaa fans.

An AIADMK source told IANS that the MLAs were in a hall of the Apollo complex. There is speculation that the party is looking at a successor to Jayalalithaa.

Crowds have been gathering outside the hospital from Sunday evening. 

Maharashtra Governor C. Vidyasagar Rao, who has additional charge of Tamil Nadu, visited the hospital on Sunday night. But he did not issue any statement after his hospital visit. 

Security has been stepped up across the sprawling state where actor-turned-politician Jayalalithaa enjoys widespread support.

A large number of people gathered outside the hospital were from the economically weaker sections. Man broke down. Some men and women, their hands folded, offered silent prayers. 

Supporters also flashed posters and photographs of Jayalalithaa, for decades the undisputed leader of the AIADMK.

Special prayers were offered in places of worships in Krishnagiri, Trichy, Tuticorin, Erode, Kanchipuram, Dharmapuri, Sivaganga and Coimbatore for the Chief Minister who was admitted to the hospital in September.

Apollo Hospitals had days ago said she was on the road to recovery and she could take a decision on going home.

As she became critical on Sunday, some parts of Chennai experienced shortages of milk as traders jacked up prices fearing a shutdown.

President Pranab Mukherjee joined the political class in wishing Jayalalithaa a "speedy recovery".

DMK chief M. Karunanidhi and his son and party leader M.K. Stalin also conveyed their best wishes for her recovery.

Congress Vice President Rahul Gandhi said: "I hope she gets better very soon," said .

Chief Ministers Mamata Banerjee of West Bengal, Devendra Fadnavis of Maharashtra, Vasundhara Raje of Rajasthan counterpart also prayed for her soon recovery.

Meanwhile, authorities in Kerala strengthened security on the border with Tamil Nadu. Police were put on alert in Thiruvananthapuram, Kollam, Idukki and Palakkad districts that border Tamil Nadu.