Basu injured his left leg after another fall at his home May 13. This prevented him from casting his vote in the Lok Sabha polls two months back. It was the first time in 63 years that he did not vote.

Former Lok Sabha Speaker Somnath Chatterjee and top CPI-M leader and state transport minister Subhas Chakraborty were among those who rushed to the hospital.

'He spoke to me. His condition has improved,' Chakraborty told reporters after coming out of Basu's room.

Born 1914 in Kolkata in a wealthy family, Basu became state chief minister in 1977. He stepped down voluntarily on health grounds in November 2000.

The last of the nine founding politburo members of the CPI-M, Basu almost became India's prime minister in 1996 as the head of the United Front government. But the CPI-M vetoed the proposal, forcing him to dub the party's decision as a 'historical blunder'.