Kumar expressed grief at the death of Tiwari and said it has caused irreparable loss to the media fraternity in the state.
"Tiwari was a humble person and a successful journalist," Kumar said in his condolence message.
"May God give strength to the family, friends and colleagues to bear with the loss of their dear one," he said.
Deputy Chief Minister Sushil Kumar Modi, Information and Public Relation Minister Vrishan Patel, RJD supremo Lalu Prasad, LJP chief Ramvilas Paswan, Youth Congress President Lalan Kumar, senior Congress leader Vijay Shankar Mishra and the Bihar Working Journalists Union mourned the death of Tiwari.
Tiwari, aged 44 years, died at a hospital in New Delhi after a brief illness.