Ukrainians abandoned inundated homes as floodwaters crested across a swathe of the south on Wednesday after the destruction of a vast hydro-electric dam on the front line between Russian and Ukrainian forces that each blamed on the other.
Residents waded through flooded streets carrying children on their shoulders, dogs in their arms and belongings in plastic bags while rescuers used rubber boats to search areas where the waters reached above head height.
Ukraine said the flood would leave hundreds of thousands of people without access to drinking water, swamp tens of thousands of hectares of agricultural land and leave more barren.
"If the water rises for another meter, we will lose our house," said Oleksandr Reva, in a village on the bank, who was moving family belongings into the abandoned home of a neighbor on higher ground. A roof of a house could be seen being swept down the swollen Dnipro River.
The Nova Kakhovka dam disaster coincides with a looming, long-vaunted counteroffensive by Ukrainian forces against Russia's invasion, seen as the next major phase of the war. The sides traded blame for continued shelling across the flood zone and warned of drifting landmines unearthed by the flooding.
Kyiv said on Wednesday its troops in the east had advanced by more than a kilometer around the ruined city of Bakhmut in eastern Ukraine, its most explicit claim of progress since Russia reported the start of the Ukrainian offensive this week. Russia said it had fought off the attack.
Oleksiy Danilov, secretary of Ukraine's national security council, said assaults under way were still localized, and the full-scale offensive had yet to begin. "When we start (it), everyone will know about it, they will see it," he told Reuters.
Kyiv said several months ago the dam had been mined by Russian forces that have controlled it since early in the 15-month-old invasion, and has suggested Moscow blew it up to try to stop Ukrainian forces crossing the Dnipro in their counteroffensive.
Residents in the flood zone in the country's south, which stretches to the Dnipro estuary on the Black Sea, blamed the bursting of the dam on Russian troops who controlled it from their positions on the opposite bank.
"They hate us," Reva said. "They want to destroy a Ukrainian nation and Ukraine itself. And they don't care by what means because nothing is sacred for them."
Russia imposed a state of emergency in the parts of Kherson province it controls, where many towns and villages lie in lowlands below the dam.
In the town of Nova Kakhovka right next to the dam, brown water submerged main streets largely empty of residents.
Valery Melnik, 53, said he had hoped for help from local authorities to pump out the water from his swamped home, but so far "they are not doing anything".
Over 30,000 cubic meters of water were gushing out of the dam's reservoir every second and the town was at risk of contamination from the torrent, Russia's TASS news agency quoted the Russian-installed mayor, Vladimir Leontyev, as saying.
Ukraine expects the floodwaters will stop rising by the end of Wednesday after reaching around five meters (16.5 feet) overnight, presidential deputy chief Oleksiy Kuleba said.
Two thousand people have been evacuated from the Ukrainian-controlled part of the flood zone and waters had reached their highest level in 17 settlements with a combined population of 16,000 people.
TASS said water levels could remain elevated in places for up to 10 days.
The mighty Dnipro River that bisects Ukraine forms the front line across the south. The huge reservoir behind the dam was one of Ukraine's main geographic features, and its waters irrigated large areas of one of the world's biggest grain-exporting nations, including Crimea, seized by Russia in 2014.
"The sheer magnitude of the catastrophe will only become fully realized in the coming days," United Nations aid chief Martin Griffiths told the UN Security Council.
Targeting dams in war is explicitly banned by the Geneva Conventions. Neither side has presented public evidence demonstrating who was responsible.
"The whole world will know about this Russian war crime," Ukrainian President Volodymyr Zelenskiy said in his nightly address, calling it "an environmental bomb of mass destruction". Earlier he said Russia blew up the hydro-electric power plant from within.
Kremlin spokesman Dmitry Peskov said on Tuesday Ukraine had sabotaged the dam to distract attention from a new counteroffensive he said was "faltering".
The United States said it was still gathering evidence about who was to blame, but that Ukraine would have had no reason to inflict such devastation on itself.
Even with the evacuation under way, Russia shelled Ukrainian-held territory across the river. Crumps of incoming artillery sent people trying to flee running for cover in Kherson. Reuters reporters heard four incoming artillery blasts near a residential neighborhood that civilians were vacating on Tuesday evening. The governor said one person was killed.
For its part, Russia said a Ukrainian drone had struck a town on the opposite bank during evacuations there and accused the Ukrainian side of continuing shelling despite the flooding.
The emptying reservoir supplies water that cools Europe's biggest nuclear power plant at Zaporizhzhia upstream. The UN nuclear watchdog said the plant should have enough water from a separate pond to cool its reactors for "some months".