Three people have died and hundreds have fled their homes in western Ukraine following the worst flooding in a decade, authorities said Wednesday.

"The situation is critical," said Prime Minister Denys Shmygal, who flew to the disaster zone with the interior minister and the head of the emergency services.

Floods caused by heavy rains that began this week hit 200 villages, damaging almost 6,000 homes, the emergency services said in a statement.

Later in the day, President Volodymyr Zelensky urged officials "to find a systemic solution, strengthen the banks of the rivers."

The worst-hit region is Ivano-Frankivsk on the Romanian border.

The flooding forced the evacuation of a hospital in the town of Galych.

A collapsed bridge in western Ukraine after heavy flooding
A collapsed bridge in western Ukraine after heavy flooding AFP / Yuriy KRYVENKO

"The situation is complicated by the fact that there are patients with the coronavirus," Prime Minister Shmygal said.

In some regions, around 70 percent of the monthly rainfall average fell over several days, said Interior Minister Arsen Avakov.

More than 100 kilometres (60 miles) of road and around 90 bridges have been destroyed, the interior ministry said.

Authorities were to start delivering food by helicopter to villages cut off by the flood waters.

The scale of this flood has already exceeded the one in 2008, when 39 people were killed in western Ukraine, Shmygal said.

Due to heavy rains on Tuesday, there was a sharp rise in the water level of the Tysa river, in some places by four or five metres.

Some experts blame large-scale and often illegal logging operations in the Carpathian mountains for removing trees that would normally help contain the run-off.