He was put on mechanical ventilator support at the critical care unit of the private hospital, UNI reported.
Bhattacharya has been suffering from COPD and other old age-related ailments for quite some time.
Chief Minister Mamata Banerjee and Governor C V Ananda Bose visited Bhattacharya in the hospital.
Bhattacharya, a senior Communist leader, remained the Chief Minister between 2001-2011.