Bosnia's only certified medicinal oxygen filling plant has been forced to close after severe flash flooding caused power outages in most of the capital.

The oxygen plant, in Sarajevo's suburbs, is crucial for the treatment of the country's seriously ill COVID-19 patients.

Avdo Delic, general manager of the Messer plant, said it was completely submerged. He voiced concern that hospitals around the country treating COVID-19 patients might run out of medicinal oxygen cylinders unless the company's operations are quickly restored at alternative locations.

"We could not save the equipment, we had to save lives," Delic said. "Water came fast like a tsunami and it is fortunate that the Civil Protection was there with rescue boats," he added.

Bosnia is seeing an increase of COVID-19 hospitalizations amid a recent surge of the virus. The country of 3.5 million has one of the lowest vaccination rates in Europe, struggling to reach at 20 percent. On Friday, it reported some 1,100 new daily infections and 32 deaths.

Heavy rain that began on Thursday evening caused the flooding, prompting evacuations, and creating power outages in most of the capital, submerging roads in some parts of the Balkan country.

Hundreds of homes in the Sarajevo suburbs, along the rivers Bosnia, Tilava and Zeljeznica, and in the southwest part of the country, around the town of Konjic, had to be evacuated.

"The situation is bad and we do not expect it to improve soon," said Danis Memagic, a firefighter coordinating evacuations in the Sarajevo suburb of Otes.

Most parts of Sarajevo were left for hours without electric power due to the flooding of one of the main substations on the outskirts of the city. The power transmission company, Elektroprijenos, said the heavy rain was hindering attempts to get the power rerouted. By Friday evening, electricity was back in most of the city.

Forecasts suggest rain will continue to fall until Sunday, raising fears of a repeat of record flooding that affected about a third of the population in 2014.