Bal Thackeray was put on life-support system on Wednesday night. Sena Spokesman Sanjay Raut said there is a slight improvement in his health on Thursday morning.
Rickshaws and taxis are largely off the roads, and even private cars are scarce, compared to the average day. Shops and other commercial establishments have voluntarily decided to stay shut.
Thousands of Shiv Sainiks waited outside 'Matoshree' for updates on the health of their leader. Policemen have been deployed at Kalanagar in Bandra (East) to maintain law and order.
BJP leader Gopinath Munde who visited Matoshree on Thursday morning also said that Sena Supremo is better than he was on Wednesday.
Political leaders, including NCP chief and Union Agriculture Minister Sharad Pawar, paid a visit to the Thackeray home. Many Mumbaikars refrained from going to work and venturing out of home as rumours about Thackeray's health were doing rounds.
Earlier, Shiv Sena executive president Uddhav Thackeray said "We are hopeful. You be hopeful.Let's pray."
Shops were closed in areas like Vakola, Shivaji Nagar, Chembur, New Bombay, Andheri, Parel which has substantial support for Shiv Sena .
Some shops were shut in other areas as many did not want to take a risk in the wake of Thackeray's health concerns.
Actor Amitabh Bachchan and his son Abhishek were injured in the melee outside Matoshree.
He said on twitter: "Yes both Abhishek and me were injured with cuts, but are fine and back home ... the doctors at 'Matoshree' attended on us !"
About Bal Thackeray's health, he said that Thackeray was a fighter and that he needed prayers right now. "When I fought for my life after Coolie accident, he came to visit me in hospital, with a cartoon he had drawn - Yamraj defeated !"
Keeping in view the health of Bal Thackeray ,heavy security has been put in place . Mumbai is on alert with 24,000 policemen in sensitive areas like Kalanagar, where Matoshree is, Dadar, Shivaji Park, Parel, Worli, Lalbaug, Currey Road, Chinchpokali and South Mumbai .
Ten platoons of the State Reserve Police Force or SRPF are being stationed at Bandra and Sena Bhavan.
This is what Bal Thackeray's son Uddhav said to people who assembled outside the ailing Shiv Sena patriarch's residence 'Matoshree' in suburban Bandra.
"Bal saheb has strong will power. We'll come out from the problem. Don't trust rumours. Make peace," Uddhav, accompanied by son Aditya, said.
Thackeray, 86, is in a "very critical" condition and he is on life support system, doctors treating the Sena leader told . As the news spread, several party workers assembled outside his residence 'Matoshree' in suburban Bandra, where security has been stepped up.
Speaking outside the residence, Sena leader Ramdas Kadam said, "Doctors are trying their level best (to stabilise Thackeray's condition) and conducting some tests on him."
MNS chief Raj Thackeray and close family members have reached Matoshree, where the Sena leader resides with his son Uddhav. A number of Shiv Sena MPs, legislators and senior leaders are also at Thackeray's residence. Police have set up barricades near Matoshree to streamline the flow of crowds.
Thackeray, who is ailing for sometime, continues to be under constant medical supervision.A team of doctors stationed inside the house with nursing staff has been taking care of the Sena patriarch, who is having breathing problems.
Last month, he could not attend his party's annual Dussehra rally in Mumbai, but addressed it through a video recorded message.
Several leaders, including former President Pratibha Patil, have visited Thackeray's residence over the past few days to enquire about his health.
Megastar Amitabh Bachchan, considered close to the Thackeray family, and his actor-son Abhishek have also reached 'Matoshree' to enquire about the Sena leader's health.