Ukraine dam: What we know about Nova Kakhovka incident

A huge dam in the Russian-controlled area of southern Ukraine has been destroyed, unleashing a flood of water.

Ukraine's military and Nato have accused Russia of blowing up the dam, while Russia has blamed Ukraine.

Thousands of people have been evacuated from communities in the surrounding areas, as catastrophic floods engulf low-lying areas either side of the river Dnipro.

Flood waters are expected to peak in the coming hours, but UN humanitarian aid chief Martin Griffiths is warning of grave and far-reaching consequences for thousands of people in the affected Kherson region.

Here's what we know so far.

The Kakhovka Hydroelectric Power Plant is in the city of Nova Kakhovka in the Kherson region. The city is currently under Russian occupation.

The dam was built in the Soviet era and is one of six that sit along the Dnipro river, which stretches all the way from the very north of the country into the sea in the south. In Kherson region, Russia occupies the left, or southern, bank while Ukraine controls the right, or northern, bank.

The dam holds back a reservoir equal in volume to the Great Salt Lake in the US state of Utah, according to Reuters. It's huge - locals call it the Kakhovka Sea as you cannot see the other bank in certain places.

Stills and video showed a massive breach in the dam, with water surging through it and flooding downstream in the direction of Kherson.

It's unclear when exactly the dam was first damaged, but satellite images suggest its condition deteriorated over a number of days.

A road across the dam appears to be damaged from 2 June, but there did not seem to be a change to the flow of the water until 6 June when the breach of the wall and collapse of nearby buildings can be clearly seen. It is currently unclear whether the damage to the road is linked to the 6 June breach.

Satellite imagery shows massive flooding along low-lying areas either side of the Dnipro river.

Images from Nova Kakhovka on Tuesday showed buildings surrounded by floodwaters and even swans paddling around a local government office.

While water levels appear now to be dropping in Nova Kakhovka, further downstream in the city of Kherson they have not yet peaked.

In the town of Oleshky, residents say some homes are almost under water, with elderly people sitting on their roofs waiting to be evacuated.

The Russian-installed mayor of Nova Kakhovka said the village of Korsunka had been completely submerged, while in three other villages - Kozachi Laheri, Krynky and Dnipryany - were flooded up to their roofs.

Hundreds of people living in low lying parts of the city of Kherson, less than 50 miles downstream from Nova Kakhovka, have been evacuated, regional governor Oleksandr Prokudin said.

He added that almost 2,000 houses on the Ukrainian-controlled right bank of the river had been submerged.

Ukrainian hydro power dam operator UkrHydroEnerho said the Nova Kakhovka station was "fully destroyed" and could not be restored.

The river has also been contaminated with 150 tonnes of industrial lubricant, said President Volodymyr Zelensky, and another 300 tonnes was at risk of leaking.

There are concerns about desertification, with agricultural land washed away by flood waters and the negative consequences of the flooding likely to be felt for years.

Ukraine's agriculture ministry said 10,000 hectares of agricultural land on the Ukrainian-controlled side of the Dnipro had been flooded, and several times more on the Russian-occupied.

At the same time some 94% of irrigation systems for agriculture in Kherson region were now without a water source, the ministry added.

It's not yet clear what caused the breach in the dam, but Ukraine's military has accused Russia of deliberately blowing it up. This seems plausible, as Moscow may have feared that Ukrainian forces would use the road over the dam to get troops across the river into Russian-held territory, as part of a counter-offensive.

But Kremlin spokesperson Dmitry Peskov rejected Russian involvement, and instead blamed Ukraine, calling it an act of "sabotage" that would deprive the Crimean peninsula - an area annexed by Russia in 2014 - of water.

Neither Ukraine nor Russia's claims have been verified by the BBC.

The dam was very important and served a number of purposes.

It held back a vast reservoir that supplied water to a host of communities upstream, and also provided cooling water to the nuclear power station at Zaporizhzhia, around 100 miles upstream, which is under Russian control and relies on the reservoir.

The International Atomic Energy Agency (IAEA) said there was no immediate nuclear safety risk but it was monitoring the situation.

It later said in a statement that if the dam did fall below 12.7m, the lowest level at which water can still be pumped upstream to Zaporizhzhia, there were alternative water sources to keep the nuclear plant cool, including a large cooling pond next to the site.

But as well as that, the dam was a vital channel carrying water from the Dnipro to Russian-occupied Crimea, meaning water supplies there are likely to be affected.

After Russia annexed Crimea in 2014, Ukraine blocked a channel carrying water from Nova Kakhovka, triggering a water crisis on the peninsula.

Russian forces reopened the channel soon after last year's full-scale invasion. But without the dam, dropping water levels could once again jeopardise the flow of water along the channel.

Russia has previously carried out several attacks on dams throughout Ukraine since the invasion, causing widespread flooding and disrupting power supplies.