"We appeal to all to remain calm and pray for him. We are grateful for the prayers and support of millions of Thackeray's admirers and supporters all over India," senior party leader Subhash Desai said as Thackeray, 86, battled breathing problems inside his home Matoshri in Bandra East.
He told journalists in the evening that a team of doctors was constantly attending on Thackeray and his condition was "gradually improving".
Earlier in the day, other leaders, including Shiv Sena MP Sanjay Raut and Maharashtra Navnirman Sena chief Raj Thackeray, also Thackeray's nephew, assured the people that his condition was "stabilizing".
"I am appealing to workers to disperse. He is absolutely stable," Raut said.
A steady stream of VVIPs, industrialists and glamour world personalities continued to visit the Thackeray residence. Amongst them were Governor K. Sankaranarayana, Chief Minister Prithviraj Chavan, Home Minister R.R. Patil, Bharatiya Janata Party (BJP) chief Nitin Gadkari and Nationalist Congress Party chief Sharad Pawar.
Glamour world personalities like Amitabh Bachchan and his son Abhishek, Rishi Kapoor with brother Randhir, Salim Khan and son Salman Khan, Manoj Kumar, Madhur Bhandarkar and Bappi Lahiri also visited Matoshri to enquire after Thackeray's delicate health.
Following the positive announcements made by several leaders, Mumbaikars relaxed though crowds of supporters continue to throng Bandra East and the entire area has remained under a security blanket.
Thackeray's son and party executive president Uddhav Thackeray made repeated appeals to the people to "maintain peace and remain calm". He had come out at 2 a.m. to address the swelling crowds, after news spread that Balasaheb's condition was critical, and said: "I have not lost hope. We are facing a crisis, we shall overcome."
Thackeray has been under the care of a team of specialists from Lilavati Hospital, Bandra West, at his home. According to party leaders, a virtual ICU had been created at Matoshri with all emergency equipment and medical and para-medical staff on duty round-the-clock.
The chief minister is understood to have discussed the security arrangements in Mumbai and the rest of the state with top police and civil officials here Thursday afternoon.
Mumbai Police and other security agencies have made heavy security arrangements outside Matoshri and in large parts of Bandra East, barely a stone's throw away from the CBD, Bandra-Kurla Complex, which also houses the US Consulate and the British Deputy High Commission.
Over 350 police personnel, Rapid Action Force and other contingents led by senior officers have deployed stringent security in the vicinity to prevent any untoward incidents.
Notwithstanding the security, tension spread.
There were reports that all shootings in Goregaon Film City had stopped and some theatres had stopped movie screenings.
Large parts of Mumbai and suburbs remained closed for businesses as news of Thackeray's delicate health spread Thursday morning.
Shiv Sena bastions like Bandra, Dadar and other parts remained virtually deserted as people preferred to remain indoors and catch the latest on Thackeray's health through the media.