By Viktoriia Lakezina

KHERSON, Ukraine Hundreds of people were evacuated from settlements along the southern stretch of Ukraine's Dnipro river on Tuesday after water burst through the breached Nova Kakhovka dam, submerging streets and town squares.

The collapse of the barrier at the southern tip of the vast Kakhovka reservoir unleashed a torrent, adding to misery for thousands of people who have been caught on the front lines of war between Ukraine and Russia.

Looking downstream, Russia controls the left bank of the Dnipro and the dam itself, and Ukraine holds the right bank. Each side has blamed the other for causing the damage that triggered the latest crisis in the conflict.

Footage posted on social media, not all of which has been independently verified by Reuters, shows severe flooding in the Russian-controlled town of Nova Kakhovka, which is next to the dam.

The town's Russian-installed mayor said water levels in the town had risen to over 11 metres and that some residents had been taken to hospital. He did not give details.

In one clip, swans swim past the ornate city council building, while in another a sports stadium next to the river is inundated.

The Russian-installed administration of Ukraine's Kherson region said it was preparing to evacuate three districts - Nova Kakhovka, Golo Pristan and Oleshky. The latter two lie across the mouth of the Dnipro river from the Ukrainian-held regional capital, Kherson.

Water levels there had already risen by more than a metre, residents said, and were expected to rise further.

"The water flow in the Dnipro River and its tributaries is very powerful," said Kherson resident Oleksandr Syomyk as he stood beside the swollen river.

"The water level rose by one metre. We'll see what happens next, but we hope for the best."

Ukrainian police released a video showing an officer carrying an old woman to safety and residents wading to safety through knee-deep water in Kherson region.

Oleksandr Tolokonnikov, a senior official at Ukraine's Kherson military administration, warned that worse was to come.

"Tomorrow there will be a peak (of flooding), then there will be a decline," he told an online media briefing.

"We already evacuated about 1,000 people. We have about 50 buses shuttling between Kherson and the affected villages. In Kherson we have four evacuation sites prepared."

The dam supplies water to a swathe of southern Ukraine's agricultural land and the Russian-occupied Crimean peninsula, as well as cooling the Russian-held Zaporizhzhia nuclear plant.

Its destruction creates a new humanitarian disaster just as Ukraine is unleashing a long-awaited counteroffensive to drive Russian troops from its territory.

(Additional reporting by Olena Harmash and Pavel Polityuk in Kyiv; Editing by Nick Macfie)