Kolkata, Jan 6 (IANS) Veteran Communist Party of India-Marxist (CPI-M) leader Jyoti Basu, hospitalised with a pneumonia attack, was in critical condition Wednesday, a medical bulletin said.

"Basu is critical. He was put on ventilator support early (Wednesday) morning as he was having respiratory problems," said the bulletin from AMRI Hospital, where a six-member medical board is treating the ailing leader.

"His condition is being monitored. All supporting medicines are being provided," the bulletin added.

The private hospital's Medical Superintendent Debasish Sharma told IANS: "His condition is serious."

Basu, 95, was hospitalised last week after a pneumonia attack and admitted to the Intensive Cardiac Care Unit of the hospital in Salt Lake, the Kolkata suburb where he lives.

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

One of the founding fathers of the CPI-M, Basu almost became India's prime minister in 1996, but the party vetoed the proposal.