Tens of thousands of people defied a nationwide coronavirus lockdown in Bangladesh on Saturday to attend the funeral of a top Islamic preacher, even as authorities battle a surge in virus cases.

Police had agreed with the family of Jubayer Ahmad Ansari, that only 50 people would attend the funeral in the eastern town of Sarail because of the risk of spreading the disease.

But local police chief Shahadat Hossain said officers were helpless to stop the crowds who came to honour the 55-year-old popular preacher and seminary head, who died on Friday. "People came in waves," he told AFP.

Organisers said some 100,000 attended the funeral. Aide to Prime Minister Sheikh Hasina, Shah Ali Farhad, also said more than 100,000 were present. Bangladesh imposed a nationwide lockdown on March 26 as coronavirus spread across the country of 168 million people.

The health department said the number of cases had risen by more than 300 on Saturday to about 2,200, while nine more deaths in one day took the toll to 84. Authorities have conducted few tests and experts say the number of cases is higher than officially recognised.

New rules ban more than five people taking part in prayers in the country's 300,000 mosques. The prime minister has called on Bangladeshis to pray at home when the Ramadan festival starts this month. But a group of influential clerics has called on Muslims to turn out in their masses for daily prayers.

Last month at least 25,000 people attended a Muslim prayer meeting in a field in the southern city of Raipur to chant "healing verses" to rid the country of the deadly virus.