In a statement, Abhishek had said doctors have diagnosed the condition and he was suffering from an intestinal obstruction.
"He has an intestinal obstruction. He is responding well to the medication. The doctors have requested for 48 to 72 hours of observation. So, we will keep him in hospital for 48 to 72 hours," Abhishek said.
Meanwhile, fans in Varanasi organised fire rituals to pray for the speedy recovery of him.
"We organised a fire ritual for long life of our beloved actor. We want him to get well soon and live many more years," said Anand Mishra, a fan.
Amitabh was taken to the Nanavati Hospital on Saturday afternoon on his 66th birthday. Later, he was referred to Lilavati Hospital.
In November 2005, Amitabh was operated on at Leelavati Hospital after he developed intestinal problems.