"Sir (Rizvi) left the hospital around 3am. He is safe and sound," Rizvi's aide 'Mazid' told bdnews24.com.
At the same time, police surrounded BNP chief Khaleda Zia's Gulshan office and stopped her from leaving the premises to join any party event. She has been confined there since.
Police say they were aware that BNP Joint Secretary General Rizvi has left the hospital.
"Rizvi was sick and was being treated there. There was no guard from our side. We heard that he left the hospital without informing the authorities," Vatara Police Station OC Sarowar Hossain told bdnews24.com.
According to those close to the BNP leader, he sneaked out of his room at the hospital around 3am, when the detective police personnel posted outside were sleeping.