"The Prime Minister has condoled the death of Shiv Sena leader Balasaheb Thackeray... The Prime Minister appealed for calm and sobriety during this period of loss and mourning," the PMO said.
Dt Singh called up Bal Thackeray's son and Sena Executive President Uddhav Thackeray to express condolences, they said.
The Prime Minister said the interests of Maharashtra were "particularly important" for Mr Thackeray and "he always strived to inculcate a sense of pride in its people."
"He founded the Shiv Sena and built the party into a formidable force in the state politics with his strong leadership. The passing away of Balasaheb will be deeply felt by his family and his followers," he said.
The Prime Minister described Bal Thackeray as a "consummate communicator, whose stature in the politics of Maharashtra was unique."
Bal Thackeray, 86, who roused emotions on Marathi pride and catapulted Shiv Sena to power in Maharashtra in the 1990s, died in Mumbai today after having been critically ill for the past few days.