BNP Chairperson Khaleda Zia was admitted to Evercare Hospital in the capital in the early hours of Saturday as she suddenly fell ill.
"Madam (Khaleda) suddenly fell ill at her Gulshan home. We rushed her to Evercare Hospital," Khaleda's physician Professor AZM Zahid Hossain told UNB.
The BNP chief was taken to the coronary care unit (CCU) of the hospital at 3:20am, he added.
Zahid, however, declined to elaborate on her illness.
The BNP chief left her Gulshan residence for the hospital at 2:55am and was admitted there at 3:15am, said her media wing member Sayrul Kabir Khan.
Hearing the news of Khaleda's illness, BNP Secretary General Mirza Fakhrul Islam Alamgir rushed to her Gulshan residence and later went to the hospital.
Coming out of the hospital around 4:30am, Fakhrul said after some primary tests, the doctors found that she has cardiac problems.
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"Madam's condition is stable now. How complicated her problem is can be confirmed after she undergoes different tests, especially an angiogram," he said.