Ukraine's prime minister on Wednesday urged the United Nations, the International Red Cross and other bodies to act immediately to help flooded residents of southern Ukraine receiving no help in areas controlled by Russian occupying forces.

"The Russian occupiers don't even make an effort to help these people, they have left them to perish," Denys Shmyhal said in English in a video posted on Telegram, referring to the aftermath of the destruction of the Kakhovka hydroelectric dam.

Tens of thousands at risk from flooding after Ukraine dam collapse

"International humanitarian organisations, on behalf of the the government of Ukraine, I urge you: you must act immediately.

"We appeal to you to take charge of evacuating people from the territory of Kherson oblast occupied by Russia, we must save the lives of people whom the occupiers have condemned to death."