Bollywood megastar Amitabh Bachchan, convalescing from a major abdominal surgery here, Thursday thanked all his well wishers and media for the concern shown towards his health.

"Amitabh has thanked the media and the people at large for showing concern for his health and extending wishes for a speedy recovery," Samajwadi Party leader and a close friend of the actor, Amar Singh said here.

"The worst is over. The diagnosis and the treatment have been done," Singh said after visiting the ailing star at the Lilavati Hospital.

The 63-year-old actor underwent a nearly three-hour-long surgery Wednesday evening by a three-member team of doctors for diverticulitis of small intestine, a condition that causes inflammation and perforation of the intestine.

He was shifted to the intensive care unit (ICU) for post-operative recovery, hospital authorities said.

The highly respected star was brought to Mumbai from New Delhi Monday, after he complained of abdominal pain, which doctors at Delhi as well as Mumbai initially diagnosed as suspected colitis.

Gastroentereologist, P. Jagannath and his team performed the operation, hospital sources said.

There had been an upsurge of emotion, sympathy and solidarity from the people across the country apart from the Bollywood fraternity, with hundreds of ordinary anxious people gathering at the hospital premises since the actor's admission.

Though many of the stars, directors and producers have visited Bachchan at the hospital in the past two days, industrialist Anil Ambani and close family members were present with him throughout.