The death toll from flooding in two Russian-controlled towns in southern Ukraine has risen to 17 one week after a massive dam holding back a reservoir was breached, a Russian-installed official said on Tuesday.

Andrei Alekseyenko, chairman of the Russian-installed administration in the Kherson region, said 12 people were confirmed dead in Hola Prystan and five in Oleshky, two small towns downstream from the breached Kakhovka dam.

Reuters could not independently verify the figures. Hundreds of people were rescued by boat from the roofs of flooded houses in the wake of the disaster, but volunteers told Russian independent media outlet iStories last week that they estimated the death toll in the hundreds.

Russia controls the south bank of the Dnipro River in Kherson region, while Ukraine holds Kherson city on the opposite bank, as well as Mykolaiv region further north.

Ukrainian Interior Minister Ihor Klymenko said on Monday that 10 people had been killed in the Kherson and Mykolaiv regions and that 42 were missing. Ukraine and Russia accuse each other of destroying the dam, which is located in Russian-controlled territory.

The Russian-installed government will begin paying compensation to flood victims on Tuesday of up to 10,000 roubles (£120), Alekseyenko said, adding that more than 500 applications have been received.

A villager in Hola Prystan told Reuters on Friday that her house was completely carried away in the torrent.

More than 7,100 people have been evacuated from areas under Russian control, including 421 children, local emergency services said.

Floodwaters have completely receded in Nova Kakhovka just south of the dam and work has begun to sanitize the area, Alekseyenko said Monday evening.

Local authorities have set up vaccination clinics against hepatitis A, typhoid and dysentery for evacuees. Samples show well water is still unsafe to drink in Hola Prystan, he said.

"Specialists have already started pumping out water and drying it with heat guns. The victims continue to receive water and food," he said.

Another top Russian-installed official, Vladimir Saldo, said more than 21,000 houses remained flooded as of Tuesday.

In volunteer-organized chat groups, family members of villagers still stuck in the flood zone clamored for fresh information about evacuations on Tuesday. Many were still unable to reach their relatives by phone and did not know where the evacuation buses were headed.

One man, Sergei, told Reuters his 83-year-old father in law spent three days in his attic in Oleshky before the water receded and he could come down.

"Dead bodies of people and animals float in the dirty water," Sergei said the elderly man related. "A stench is beginning to rise over the town."