Rizvi complained of chest pain as he got into his car after joining a human-chain programme in front of the Jatiya Press Club at noon, said his personal assistant Arifur Rahman Tushar.
The BNP leader was first taken to Islami Bank Central Hospital at Kakrail.
Later, he was taken to Labaid Hospital in the city’s Dhanmondi area where he has been kept in its CCU.
Dr AZM Zahid, former secretary general of Doctors Association of Bangladesh (DAB), said Rizvi suffered a heart attack. “His condition is now critical. Nothing can be said about his condition as he is now under close observations.”
Meanwhile, BNP secretary general Mirza Fakhrul Islam Alamgir visited Rizvi at the Labaid Hospital.
He enquired about his health condition from doctors and talked to Rizvi’s wife, Anjumanar Begum.
Talking to reporters, Fakhrul said, "I’ve talked to doctors. We’re hopeful... he'll recover soon.”