Ten patients died after a fire broke out at a Mumbai mall hospital where coronavirus patients were being treated, a fire brigade official said on Friday.

The fire broke out at the Sunrise Hospital in the Dreams Mall building in Bhandup area shortly after midnight, the official said. Around 70 patients were rescued, he added.

The hospital said there were two deaths due to COVID- 19 at the facility and there was no death due to the fire.

The hospital is situated on the top floor of the four-storeyed mall building and 76 patients, most of them being treated for COVID-19, were there when the fire broke out, the official said.

The cause of the 'level four' fire (serious emergency call in fire brigade parlance) has not been ascertained yet, the BMC control room sources said.

Twenty fire engines, 15 water tankers and ambulances were rushed to the spot. Fire fighting operation is underway, the official said.

The 70 patients were evacuated by the fire brigade and shifted to another hospital, the official said, adding fire personnel are checking if any patient is still stuck there.

Maharashtra Chief Minister Uddhav Thackeray said strict action will be taken against those found responsible for the fire.

Mumbai Mayor Kishori Pednekar who visited the site expressed surprise that a hospital was operating inside the mall.

"I have seen a hospital at a mall for the first time," the mayor said, adding action will be taken if irregularities were found in allowing the facility to operate there.

The hospital in a statement said, "There was a fire on the first floor of Dreams Mall, Bhandup and the smoke reached up to the Sunrise Hospital located on the top floor. When fire alarms beeped, all patients were safely evacuated to the fire refuge area as the smoke was reaching the hospital."

"The two bodies have been shifted as well. The other patients have been shifted to nearby jumbo COVID-19 centre and private hospitals," the hospital said.

The statement said the hospital was started last year in "exceptional circumstances" of the pandemic and has helped save many lives. "The hospital is functioning with all due compliances like fire licence, nursing home licence among others," it said.

The chief minister further said the state government had last year allowed some hospitals to treat COVID-19 patients given the spread of the disease and said that the facility in the Bhandup mall was one of them.

"The permission was to end on March 31. Unfortunately, the fire broke on the first floor of the mall and spread upwards," he said.

The chief minister said that efforts were made to rescue all the patients admitted at the hospital. However, it took some time to evacuate those who were on ventilators.

"Unfortunately, they died," he said."We wake up after such incidents take place and then a probe is carried out. This incident, too, will be investigated. Action will be taken as per law probe against whoever is at fault," Thackeray added.

"I had asked (the authorities) to ensure such incidents do not occur. Still, unfortunately, this has taken place.

"...I express regret to those who have lost their kin in the incident," he said in Marathi.

Speaking in Hindi, Thackeray later said, "I apologise to the kin of those who died in the incident."

The chief minister said that compensation of Rs 5 lakh will be given to the next kin of each deceased.

President Ram Nath Kovind expresses grief over the incident.

"Deeply mourn the loss of lives in a fire accident at a hospital in Bhandup, Mumbai. My thoughts and prayers are with the families of the victims of this tragedy. I pray for speedy recovery of the injured," he tweeted.