The patients, aged between 45 and 75, were admitted to the hospital with Covid-19 like symptoms and were being treated at the isolation ward outside the main hospital building, United Hospital authorities said in a statement.
The hospital authorities in the statement also speculated that the fire originated from short circuit and spread immediately as it was windy outside due to bad weather.
Fire service officials are investigating the cause of the fire and the hospital authorities are fully cooperating with them to this end, the statement read.
"We found five bodies -- four male and one female. All were patients of the hospital," Lt Col Zillur Rahman, director (operations) of Fire Service and Civil Defence told.
"The bodies were recovered after the fire was doused," he added.
The deceased patients were aged between 45 and 75 years, said Abul Kalam Azad, station officer of Baridhara Fire Service Station.
Firefighters brought the blaze under control around 10:05pm after it broke out at the hospital around 9:50pm, said Kamrul Islam, a duty officer at Fire Service and Civil Defence Headquarters.
The blaze was doused around 10:30pm, he added.
The fire broke out at the Corona Isolation Unit of the hospital on the ground floor, said SM Kamruzzaman, officer-in-charge of Gulshan Police Station.
"We informed the fire service immediately and brought the fire under control soon after it broke out with the hospital's own fire extinguishing system," the United Hospital statement read.
"We, on behalf of the hospital's doctors, nurses and staff, express deep shock and grief at the loss of lives in the tragic incident," it said.
Steps have been taken to ensure security of the patients being treated at the hospital, the statement added.
