The United Nations on Sunday accused Russia of blocking humanitarian aid to Moscow-controlled areas of eastern Ukraine that have been devastated by the flood caused by the Kakhovka dam blast.

Thousands of people were forced to flee settlements downstream in the Kherson region, and the flood has also decimated farms and entire ecosystems.

"The government of the Russian Federation has so far declined our request to access the areas under its temporary military control," the UN humanitarian coordinator for Ukraine, Denise Brown, said in a statement.

"The UN will continue to do all it can to reach all people — including those suffering as a result of the recent dam destruction — who urgently need life-saving assistance, no matter where they are," Brown added.

"We urge the Russian authorities to act in accordance with their obligations under international humanitarian law."

The humanitarian impact has been severe on both sides of the Dneiper River.

Ukraine's Interior Minister Ihor Klymenko said 17 people had died from the dam blast in territory held by by the Ukrainian government, with another 31 people still missing.

He said nearly 900 homes remained under water and more than 3,600 people had been evacuated.

Meanwhile, the head of the Russian-installed administration that controls part of Kherson, Andrei Alekseyenko, said the death toll had risen to 29 people.

Ukraine and Russia have blamed each other for the blast. A team of international experts said on Friday it was "highly likely" the destruction of the dam was caused by explosives planted by Russians.

Ukraine claims progress in Avdiivka

Ukrainian troops have gained ground near the front line city of Avdiivka, according to Kyiv.

"The Avdiivka sector is very effective in repelling assaults," Ukrainian President Volodymyr Zelensky said in his nightly address on Sunday.

The head of the military administration in Avdiivka also told national television that Ukrainian forces had advanced about one kilometer (two-thirds of a mile) around the town over the past two weeks.

Zelensky : Russia should prepare citizens for defeat

Russia should prepare its citizens for the prospect of losing more occupied Ukrainian territory, Zelensky said in his nightly address on Sunday.

He said that "there is no alternative and there will be none" to Russian troops withdrawing from Ukraine's borders.

Zelensky said Ukrainian troops were gradually liberating settlements and that Ukraine is expecting its Western allies to pledge more military assistance in the coming week.