Veteran CPI(M) leader Harkishan Singh Surjeet was taken off the ventilator on Tuesday following some improvement in his condition though it still remains "critical".

"He was completely off the ventilator the whole day. We have not given him any support in the form of any medicine or any mechanical support. Still then he is maintaining oxygen saturation. This is one big improvement that has happened after he was admitted here," Dr Purushottam Lal, who is monitoring him, said.

The 92-year-old former general secretary of the CPI(M) was admitted to the Metro Hospital in Noida on May 6 following a severe cardiac-respiratory arrest.

Dr Lal said Surjeet's blood pressure, urine output and heart beat had been reported to be normal the whole day.

The veteran leader responded to "painful stimuli" and is breathing on his own, but his condition is still "critical", Dr Lal said.

"There was also an occasional blinking of the eye and jaw movement," he said.

Leader of the Opposition in Lok Sabha L K Advani, Delhi Chief Minister Sheila Dikshit,  Union Minister Ram Vilas Paswan and JD(U) leader Sharad Yadav visited the ailing leader.