low canal
© Pierre Crom/Getty ImagesNorth Crimean Canal • Low water table
Around 700,000 people living in Ukraine's southern Kherson region now urgently need access to drinking water after a major dam breach this week, the UN has said. Western intelligence officials said that record low water levels in the Kakhovka Reservoir after its dam burst on Tuesday have dried up a canal that supplies occupied Crimea with fresh water.

The warnings come as Ukraine's army pushes its counteroffensive, aimed at recapturing Crimea, which the Kremlin annexed in 2014.

Martin Griffiths, the UN Under-Secretary General for humanitarian affairs and its emergency relief coordinator, said the collapse of the dam had triggered an "extraordinary" humanitarian crisis that has forced thousands of people from their homes and destroyed vital infrastructure.

"You've got a huge, looming problem of a lack of proper drinking water for those 700,000 people," he said in an interview with US media.

Mr Griffiths said he expected water-borne diseases to spread and that the flooding would worsen a global grain shortage triggered by the war.

"The truth is this is only the beginning of seeing the consequences of this act," he said.

Ukraine has accused the Kremlin of destroying the dam. The Kremlin has denied this.

The lack of water in the Kakhovka Reservoir will also hit Crimea because it relies on a 250-mile Soviet-built canal from the reservoir for much of its water

The pro-Russia authorities in Crimea have said water is still running through the canal and that the region has plenty of reserves, but the British Ministry of Defence said that water levels at the reservoir had now dropped below the level of the inlet that feeds the canal.

"Russian authorities will likely meet the immediate water requirements of the population using reservoirs, water rationing, drilling new wells, and delivering bottled water from Russia," it said in an intelligence update.

Three people were killed and another 10 hurt when Russia shelled a rescue boat evacuating people after the flood, regional authorities said on Sunday.

"Three civilians were killed, another 10 were injured, including two law enforcement officers," said the governor of the Kherson region, Oleksandr Prokudin.