KHERSON, Ukraine >> Five residents of a Russian-occupied city next to a breached dam have died in massive flooding triggered by the catastrophe, its Kremlin-appointed mayor said Thursday, the first official report of deaths from one of the largest environmental crises since Russia’s invasion of Ukraine more than 15 months ago.

Vladimir Leontyev, the Russian-appointed mayor of Nova Kakhovka, told Russian state TV that two other people who had gone missing following Tuesday’s dam breach had been found, and efforts were underway to evacuate them.

Officials say at least 4,000 people have been evacuated from both the Russian and Ukrainian-controlled sides of the Dnieper river, which has become part of the front line between the fighting forces.

On the Ukrainian-controlled western bank, Ukrainian President Volodymyr Zelenskyy arrived Thursday to evaluate the response to damage caused by the dam breach. He wrote on his Telegram account that he was helping assess efforts to evacuate civilians, provide them with drinking water and other support, and try to stanch vast environmental damage.

Zelenskyy also raised the prospect of financial aid for residents and businesses driven from their homes and offices by the rising waters.

Regional Governor Oleksandr Prokudin said the average level of flooding Thursday morning in the region was more than 5.6 meters (18 feet) and roughly 600 square kilometers (231 square miles) of the region were submerged — more than two-thirds of that on the Russian-controlled eastern bank.

The true scale of the disaster is yet to emerge in an affected area that was home to more than 60,000 people.

The dam and associated reservoir, which are essential for fresh water and irrigation for southern Ukraine, lie in the Kherson region that Moscow illegally annexed in September — and parts of which Russian forces have occupied for the past year.

The reservoir is also critical for water supplies to the Crimean Peninsula, which Russia illegally annexed in 2014.

French President Emmanuel Macron tweeted that the destruction of the dam was an “attack” and an “atrocious act,” without saying who is to blame. Paris said it was rushing aid including water purifiers, 500,000 water purification tablets and hygiene kits to help people displaced by the disaster.

Ukrainian officials have accused Russia of purposely destroying the dam, which is located in an area controlled by Russian forces.

President Alexander Lukashenko of Belarus, a key ally of Russian President Vladimir Putin, backed the Russian claim that Ukraine blew up the dam to distract attention from what it described as a botched Ukrainian attempt to launch a counteroffensive.

“They needed to cover up the three days of their ‘counteroffensive’ in which they lost nearly 200 armored vehicles and more than 2,000 troops,” he said during Thursday’s meeting with officials. “And so it’s all about Kakhovka and no one is talking about that. It’s quite obvious.”