The Tamil chief minister suffered a heart attack on Sunday evening.
Tamil Nadu Chief Minister Jayalalithaa was said to be critical late on Sunday night after she suffered a cardiac arrest in the hospital where she was admitted over two months ago.
"The honourable Chief Minister of Tamil Nadu, who is undergoing treatment at Apollo Hospitals, suffered a cardiac arrest this evening," said a statement issued by Apollo Hospital, where she was admitted on September 22.
"She is being treated and monitored by a team of experts, including cardiologists, pulmonologist and critical care specialists," Chief Operating Officer and head of transformation of Apollo Hospital Dr Subbaiah Viswanathan said in the statement on Sunday.
Dr Richard Beale from London has also been consulted and concurred with line of treatment by our cardiologists & pulmonologists, the hospital said.
Around midnight, Apollo Hospital's Joint Managing Director Sangita Reddy tweeted: "The Apollo TN CM #Jayalalita is critical.multi speciality team @hospitalsapollo trying everything including ecmo.praying for her recovery."
Soon after the Apollo statement came, Union Home Minister Rajnath Singh spoke to Tamil Nadu Governor Ch Vidyasagar Rao and enquired about Jayalalithaa's health.
Rao, who is also Governor of Maharashtra, rushed to Chennai from Mumbai and went to the hospital. The governor was at the hospital for some time, after which he went to the Raj Bhavan past midnight.
Ministers and top police officials also rushed to the hospital and held informal consultations on the situation.
Heavy deployment of police was made at the hospital on Greams Road where thousands of supporters of Amma (mother), as she is fondly called by her supporters, and AIADMK cadre had gathered on hearing the news.
In a communication to ADGPs of Enforcement, CB-CID, Economic Offences Wing and Crime wings, the Director General of Police's office asked them to "mobilise all the officers in the rank of SPs and police personnel of other ranks of Enforcement, CBCID, EOW and Crime completely and they should report" to SPs and Commissioners of Police at 7am.
"They should report in full uniform with their vehicles for law and order bandobust duty until further orders," it said.
President Pranab Mukherjee, DMK leader M Karunanidhi, his son and opposition leader K Stalin, Union Ministers, Congress leader Rahul Gandhi, Chief Ministers and a host of leaders expressed concern over Jayalalithaa's health condition and wished her speedy recovery.
Meanwhile, home ministry officials are in constant touch with Tamil Nadu government officials and assessing the situation.
The central government will provide all assistance to the Tamil Nadu government if any help is required, sources said.
Nine companies of the Rapid Action Force have been put on standby to be immediately airlifted from various places in the country to Tamil Nadu, if needed, senior officials said. Each RAF company consists of around 100 personnel.
Sources indicated that the chiefs of two central paramilitary forces -- Central Reserve Police Force Director General K Durga Prasad and Central Industrial Security Force DG O P Singh -- could be sent to Tamil Nadu to supervise security deployment, if any need arises.
Large number of AIADMK supporters thronged Apollo Hospitals on Sunday night. Heavy police deployment has been made in and around the hospital.
Police were seen controlling the stream of people to prevent any untoward incident even as they blocked the main road leading to the hospital.
Barricades have been set up in the vicinity of the hospital and police presence could be seen in arterial roads near the hospital.
Many women, who gathered near the main gate of the hospital, could be seen praying fervently for the well-being of their 'Amma' (as Jayalalithaa is fondly called by AIADMK cadres, meaning mother).
"I only hope to hear good news about Amma's health. Right now, we are very tense. I got the news about her heart attack one hour back and just arrived here," an AIADMK cadre told PTI.
Some of the women held photographs of Jayalalithaa and raised slogans "Amma vaazhga, Puratchi thalaivi vaazhga!! (Long live Amma, Long live the revolutionary leader)."
Last week Apollo Hospitals Chairman Dr C Pratap Reddy announced that Jayalalithaa was doing well and speaks using a valve attached to the tracheostomy tube as she continues to get treatment.
Whole body physiotherapy was being done, Dr Reddy had said, adding that she was normally recuperating after being in bed for several weeks and would herself decide when to go home.
Jayalalithaa was hospitalised on September 22 after she complained of fever and dehydration.
The hospital, which had been issuing bulletins on her health status, later said she was being treated for infection with respiratory support, among others.
Earlier on Sunday, AIADMK spokesperson C Ponnaiyan told reporters that a three-member expert team from the All India Institute of Medical Sciences, Delhi, had said she had completely recovered.
"The AIIMS doctors visited the hospital yesterday and after examining her health, they shared the good news with us that Amma has completely recovered," he had said.
The chief minister, Ponnaiyan said was doing physical exercises, undergoing physiotherapy, and was having food on her own besides advising officers on issues related to government and party activities.
In May the 67-year-old Jayalalithaa led the All India Anna Dravida Munnetra Kazhagam to a resounding victory in the state assembly elections,
