More than 1,000 people have been evacuated from the southern Ukrainian city of Kherson and other Ukrainian-held parts of the wider region following the collapse of the Nova Kakhovka dam, a local official said Tuesday on the Telegram messaging app.

Oleksandr Prokudin, the Ukrainian governor of the Kherson region, said that 1,364 people had been evacuated from flooded areas, including 1,221 people from the Ostriv district of the regional capital, as of Tuesday evening local time.

The official also said that more than 1,000 houses in the Ukrainian-held parts of Kherson region “appear to be underwater."

Prokudin said he understood the settlements of Korsunka and Dnipriany on the east bank of the Dnipro river – occupied by Russia – were “fully flooded” and others —Krynky, Kozachi Laheri, Pishchanivka, Oleshky, Kardashynka, Hola Prystan and Stara Zburiivka – were “partially flooded”.

In an earlier Telegram post, Prokudin said that dozens of houses in the region had been flooded.

“The water continues to come and flood the settlements of Kherson region. As of now, 71 houses are known to be flooded,” he said. “In the village of Tiahynka alone, 2 bridges and 33 houses are flooded. In Burhunka, 3 houses are under water. In Odradokamyanka, a bridge is flooded, making it difficult to get to the settlement. In the village of Kozatske, 30 houses are flooded.”

More background: The critical Nova Kakhovka dam is the largest reservoir in Ukraine in terms of volume. It’s the last of the cascade of six Soviet-era dams on the Dnipro River, a major waterway running through southeastern Ukraine. There are multiple towns and cities downstream, including Kherson, a city of some 300,000 people before Moscow’s invasion of its neighbor.

It is unclear what caused the dam to collapse, which came as Ukraine geared up for a widely anticipated counter-offensive. Both Ukrainian and Russian officials said the dam collapsed in an explosion and are blaming each other for it.