Apollo had tweeted on Sunday night that Jayalalithaa was "critical", that she was being closely monitored. Photograph: (AFP)
Jayalalithaa, who was the chief minister of India's southern state of Tamil Nadu, had been hospitalised for over two months
Indian politician Jayalalithaa Jayaram has passed away following a cardiac arrest, Apollo Hospital announced on Monday night. According to a press release from the hospital, the time of her death was recorded at 11.30 pm local time.
Jayalalithaa, who was the chief minister of India's southern state of Tamil Nadu, had been hospitalised for over two months.
She had complained of dehydration and fever on September 22 and was admitted to Apollo Hospital in Chennai, the capital city of Tamil Nadu state.
Jayalalithaa suffered a cardiac arrest on Sunday evening, hours after her party members said her health had become better and was currently undergoing physiotherapy.
Apollo Hospital in Chennai issued a statement later, saying the 68-year-old satrap was being monitored by a team of experts including cardiologists, pulmonologist and critical care specialists.
On Monday afternoon, a hospital spokesperson said Jayalalithaa remained "very critical" and was on a heart-assist device and other life-support systems.
Thousands of her well-wishers gathered outside the hospital after news broke out about her cardiac arrest. Many of them camped outside the hospital overnight, as did several of her party members.
In a late night oath taking ceremony at around 1.30 am local time, a new cabinet took pledge with O Panneerselvam being sworn-in as the next chief minister of Tamil Nadu.
Senior AIADMK leader O Panneerselvam takes oath as the next CM of Tamil Nadu pic.twitter.com/8iwCls0pey— ANI (@ANI_news) December 5, 2016
The hospital remains cloaked in a thick blanket of security as there are fears about an outbreak of violence in the city.
The state police chief, TK Rajendran, meanwhile has ordered all police personnel to report for duty "until further orders".
Nine companies of the Central Reserve Police Force have also been put on standby.
Indian Prime Minister Narendra Modi, who enjoyed a good personal equation with Tamil Nadu Chief Minister J Jayalalithaa, expressed deep sadness over her demise and said it has left "a huge void in Indian politics".
Hailing the AIADMK supremo who passed away at a Chennai hospital tonight, Modi said her connect with citizens, concern for welfare of the poor, the women and marginalised will always be "a source of inspiration".
He said he would always cherish the innumerable occasions when "I had the opportunity to interact with Jayalalithaaji. May her soul rest in peace."
In a series of tweets, the Prime Minister said, "Deeply saddened at the passing away of Selvi Jayalalithaa. Her demise has left a huge void in Indian politics.
"My thoughts and prayers are with the people of Tamil Nadu in this hour of grief."
I will always cherish the innumerable occasions when I had the opportunity to interact with Jayalalithaa ji. May her soul rest in peace.— Narendra Modi (@narendramodi) December 5, 2016
May the Almighty grant them the strength to bear this irreparable loss with courage and fortitude.— Narendra Modi (@narendramodi) December 5, 2016
My thoughts and prayers are with the people of Tamil Nadu in this hour of grief.— Narendra Modi (@narendramodi) December 5, 2016
Jayalalithaa ji’s connect with citizens, concern for welfare of the poor, the women & marginalized will always be a source of inspiration.— Narendra Modi (@narendramodi) December 5, 2016
Preetha Reddy, owner of Apollo where Jayalalithaa had been admitted said "Devastating loss to the state and the nation. J Jayalalitha was an iconic leader. A humane visionary. A personal friend for years. Will miss her presence immensely."
A seven-day state mourning starting December 6 has been declared in Tamil Nadu. Schools and colleges in the state will remain shut for three days.
The politico's mortal remains were taken to her home in Poes Garden, with supporters and party workers chasing the ambulance and trying to touch it. A scuffle broke out between the police and party workers. Many tried to break the barricades and the police resorted to a baton charge.
On Monday evening, Apollo Hospital had to repudiate rumours of Amma's death after several news outlets erroneously began flashing news about her demise.
The hospital, in their clarification letter, stated that news of her death were "baseless and false". They insisted that she remained on life-support system.
Even some prominent Urdu publications in Pakistan reported that the 68-year-old leader had passed away.
Jayalalithaa, fondly known as 'Amma' (mother) by her supporters, is treated like a demi-god in her home state.
Jayalalithaa joined the All India Anna Dravida Munnetra Kazhagam (AIADMK) in 1982.
Jayalalithaa acted in several movies before joining politics and had a huge fan following.
She wielded national influence, with her party holding the third-largest number of seats in the Lok Sabha (lower house of India's Parliament).
Her domineering status in the party, often perceived by her critics as a one-woman party, means there is no clear candidate to take over the party reins.
(WION with inputs from agencies)