Ola, 86, will be accorded a state funeral at his home district Jhunjhunu in Rajasthan Monday.
Top dignitaries, including President Pranab Mukherjee, Vice President Hamid Ansari and Congress chief Sonia Gandhi, condoled his death while the cabinet met to mourn passing away of the veteran leader.
As a mark of respect to Ola, the national flag was flown at half-mast on all government buildings in Delhi and all state and union territories Sunday and will also be flown likewise at Jhunjhunu Monday.
The veteran Congress leader was admitted to the Medanta Hospital around 45 days ago, officials from the hospital and his office said.
"He died at 4 a.m. Sunday due to heart failure," his office told IANS.
Ola is survived by his wife Shiv Bai, sons Bijender and Surjeet and daughter Chandrakala.
Born July 30, 1927, the Jat leader was a member of the Rajasthan assembly from 1957 to 1990 and served as minister from 1980 to 1990.
He received the Padma Shri in 1968 for social work.
He was elected to the Lok Sabha for the first time in 1996 and then again in 1998, 1999, 2004 and 2009.
Ola was appointed a cabinet minister in June this year, in the hope of political gains in the Rajasthan assembly elections in November, but the Congress was routed, losing power to the Bharatiya Janata Party.
Earlier, Ola was a minister in the United Front governments of H.D. Deve Gowda and I.K. Gujral, holding independent charge of chemicals and fertilisers from 1996 to 1997 and of water resources from 1997 to 1998.
He was a minister in the first United Progressive Alliance (UPA) government, holding charge of labour and employment, from May 23, 2004, to Nov 27, 2004.
His son Bijender is a legislator from Jhunjhunu and a former minster in the Rajasthan government.
His second son, Surjeet, runs a school - Indira Gandhi Balika Niketan - in his native Ardawata village of Rajasthan.
In a condolence message to his wife, the president said: "I am deeply saddened to learn about the passing away of Sis Ram Ola who was a friend and colleague of long years."
"In his death, the nation has lost an eminent leader and social worker who was always in touch with the grassroots of society," he added.
Ansari said that Ola was a popular political leader "who was intimately connected to the masses".
"Ola served the people of our country and his home state of Rajasthan with dedication and distinction, as a member of Lok Sabha and Rajasthan Vidhan Sabha for several terms and also as member of the union and state cabinet," he said.
In her message, Sonia Gandhi said: "A grassroots leader who fought for the cause of people, Ola had a solid connect with his constituency and his invincible electoral record reflected the same."
Terming Ola "a valued member", a cabinet statement said that he "was a grassroots political leader with extraordinary sensitivity to the people".
"He left an indelible mark in the ministries he worked with his commitment and able leadership. Ola handled his public responsibilities with tact, politeness and grace. He was held in very high esteem across the political spectrum. In his death, the country has lost a popular leader," it added.
--IANS (Posted on 15-12-2013)