"I am deeply saddened at the passing away of Sis Ram Ola, a popular political leader who was intimately connected to the masses," Ansari said.
He said in a long and distinguished public life spanning over five decades, Ola served the people of the country and his home state of Rajasthan with dedication and distinction.
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He served as a Member of Lok Sabha and Rajasthan Assembly for several terms, and also as Member of the Union and State Cabinet, the Vice President said.
The Prime Minister also expressed grief at the demise of the 86-year-old Congress leader, who had been suffering from various ailments.
"He was a valued colleague and a dedicated social worker," the PMO said on social networking site Twitter.
Sonia Gandhi expressed deep grief over Ola's death, saying, "The Congress party, the state of Rajasthan, as indeed the nation, has lost a leader of stature and rare earthy wisdom."
Extending condolences to the bereaved family, she said Ola was a grassroots leader who fought for the cause of the people and had a solid connect with his constituency, as was reflected by his invincible electoral record.
Singh and the Congress president also visited Ola's residence and offered condolences to the senior Congress leader's family.
"The Prime Minister has called a special meeting of the Cabinet to pay condolences to Shri Sis Ram Ola, Union Minister for Labour and Employment," the PMO said in another tweet.
The senior Congress leader is survived by his wife, two sons and a daughter. Ola was awarded Padma Shri for social work in 1968.