"His death has caused irreparable loss to politics and society", Kumar said in a condolence message.
"I pray that God will give enough strength to his family and followers in this hour of sorrow", he said.
Kumar recalled Deshmukh's contribution to the nation and particularly to a state like Maharashtra.
Meanwhile, Bihar Youth Congress activists led by its president Lalan Kumar held a condolence meeting and remembered Deshmukh for his contribution to the party.
Lalan Kumar said it was a great loss to the Congress and people of Maharashtra.
"Deshmukh will always be remembered for his contribution for the uplift of the poor and dedicated service to the nation", Lalan Kumar said.
Former Congress Legislature Party leader in Bihar Legislative Council Vijay Shankar Mishra, party leaders Subodh Kumar and Rohit Paswan also condoled the death.
Lalan Kumar said he would participate in the funeral of Deshmukh.