Veteran Marxist leader Jyoti Basu's health condition further deteriorated Thursday and he has been put on dialysis, hospital authorities said.

'Basu's condition is very critical. He is still on ventilator support. The oxygen requirement for his body has also increased. He has been put on dialysis.

'The heart and renal functioning have further worsened today (Thursday). His blood pressure is now being maintained through medicine,' said a medical bulletin released this evening by the hospital authorities. The report said the dialysis would continue for next four hours.

The former West Bengal chief minister was hospitalised Jan 1 after a pneumonia attack. 'The expert team is constantly monitoring the ailing 95-year-old leader. The AMRI medical board will again meet tomorrow (Friday) at 9.30 a.m. to review his health condition,' it pointed out.

Earlier, AMRI medical superintendent Debashis Sharma said Basu's urine output had come down in the morning.

The Communist Party of India-Marxist (CPI-M) leader was admitted to the Salt Lake hospital near his residence Indira Bhavan Jan 1 after a pneumonia attack. He was shifted to the Intensive Cardiac Care Unit (ICCU) the next day and put on ventilator support Jan 6 following acute respiratory problems.

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