MOSCOW/KYIV, June 6 (Reuters) - Blasts at a Soviet-era dam in the Russian controlled part of southern Ukraine on Tuesday unleashed floodwaters across the war zone, according to both Ukrainian and Russian forces who blamed each other for blowing-up the dam.

Unverified videos on social media showed a series of intense explosions around the Kakhovka dam. Other videos showed water surging through the remains of the dam with bystanders expressing their shock, sometimes in strong language.

The dam, 30 metres (yards) tall and 3.2 km (2 miles) long and which holds water equal to the Great Salt Lake in the U.S. state of Utah, was built in 1956 on the Dnipro river as part of the Kakhovka hydroelectric power plant.

It also supplies water to the Crimean peninsula, annexed by Russia in 2014, and to the Zaporizhzhia nuclear plant, which is also under Russian control.

Russian-installed officials said there was no danger yet to the Zaporizhzhia nuclear plant, Europe's largest nuclear power plant, from the destruction of the dam. The nuclear power station gets its cooling water from the reservoir.

Ukraine's military said that Russian forces blew up the dam while Russian sources blamed Ukraine.

"The Kakhovka (dam) was blown up by the Russian occupying forces," the South command of Ukraine's Armed Forces said on Tuesday on its Facebook page.

"The scale of the destruction, the speed and volumes of water, and the likely areas of inundation are being clarified."

Russian news agencies said the dam, controlled by Russian forces, had been destroyed in shelling while a Russian-installed official said it was a terrorist attack - Russian shorthand for an attack by Ukraine.

The Russian installed head of the Kherson region said evacuation near the dam has begun and that water would reach critical levels within five hours.

Reuters was unable to immediately verify the battlefield accounts from either side.

Ukraine's President Volodymyr Zelenskiy will hold an emergency meeting over the Nova Kakhova dam blast in southern Ukraine, Oleksiy Danilov, secretary of Ukraine's National Security and Defence Council, said on Twitter on Tuesday.

It was not immediately clear how the flood waters would affect Ukraine's long planned counter-offensive against Russian forces who are dug in across southern and eastern Ukraine.