CPI leader AB Bardhan, who lived in the CPI office, died in New Delhi on Saturday.
The CPI(M) today expressed "deep grief" over the death of CPI leader AB Bardhan, describing him as a "veteran leader of the Communist and working class movement of India".
As general secretary of the Communist Party of India, Bardhan helped to build Left unity, the Communist Party of India-Marxist said in a statement.
"He played a key role in strengthening relations with CPI(M). Bardhan's life and work was that of a dedicated Communist leader. In his death, the CPI and the Left movement have lost an invaluable leader."
Mr Bardhan, who lived in the CPI office, died in New Delhi on Saturday.