Former Kerala chief minister E K Nayanar died in New Delhi on Wednesday after protracted illness, Communist Party of India-Marxist sources said.
The 87-year-old leader died at around 1700 IST.
The CPI-M veteran was admitted to the All India Institute of Medical Sciences on April 26 for treatment of diabetes and foot ulcer.
On May 6, both his kidneys failed and he suffered a massive heart attack. An angioplasty was done and a block in the heart valve was removed. He was on life-support system since then.
CPI-M politburo members Prakash Karat, Sitaram Yechury and S Ramachandran Pillai have gone to the hospital.