Chief Minister Mamata Banerjee also visited Bhattacharjee.
The 75-year-old leader, suffering from the progressive lung problem chronic obstructive pulmonary disease (COPD), was being treated at his Palm Avenue residence for long, but hospitalisation became necessary as his condition deteriorated and blood pressure fell.
"No rumours. He is fine. His condition is stable," Communist Party of India-Marxist (CPI-M) politburo member Mohammad Salim told mediapersons at the hospital on Friday night.
A medical board has been formed for Bhattacharjee's treatment.
Bhattacharjee, suffering from the disease for years, now has to frequently resort to oxygen support for breathing properly. He also has a severe eye problem.
For the first time in decades, Bhattacharjee had failed to cast his vote in the Lok Sabha polls in May due to indisposition.
Bhattacharjee was seen last in public on February 3, when he went to the Brigade Parade ground to attend a rally called by the Left Front.
However, his was only a token presence, as he was not permitted by the doctors to step out of the car because of the dust on the ground. He returned home after spending some time in his vehicle at the ground.
Bhattacharjee, who was the Bengal Chief Minister during 2000-2011, undertook an all-out industrialisation drive for reducing unemployment in the state but the measure proved counter-productive.
As his government tried to acquire large land masses for setting up industries, the farmers revolted, and the Trinamool Congress fanned the discontent to gain popularity and finally came to power in 2011 ending 34 years of the Left Front rule.