Veteran Tollywood actor Krishna was hospitalised after he suffered a cardiac arrest on Monday.
Doctors at Continental Hospital said that his condition is critical but somewhat stable. The next 24 hours will be critical, Hospital Managing Director Guru N. Reddy.
The actor is undergoing treatment in the Intensive Care Unit and is on a ventilator, doctors said.
They said that Krishna, father of popular actor Mahesh Babu, was brought to Continental Hospital in Gachibowli around 2 a.m. in an unconscious state after he suffered a cardiac arrest.
"The cardiologists immediately performed CPR and in 20 minutes he was brought out of cardiac arrest," Reddy said.
A team of doctors including cardiologists and critical care specialists were keeping a close watch on his condition.
The doctors made it clear that they can't say anything about the outcome for next 24 hours or 48 hours.
All close family members of the veteran actor rushed to the hospital.
The veteran actor, whose full name is Ghattamnaneni Siva Rama Krishna Murthy, turned 79 in May this year.
The superstar of yesteryears was reported to be depressed since the death of his wife Indira Devi in September. In January, he lost his elder son Ramesh Babu.
As the word spread about Krishna's hospitalisation, messages poured in from all over for his speedy recovery.
In a career spanning five decades, Krishna acted in more than 350 films. In 2009, he was honoured with the Padma Bhushan for his contributions to Indian cinema.