Volkswacht Bodensee - Leave 'immediately', pro-Russian officials tell Kherson residents

It comes as President Volodymyr Zelensky said Russia had launched 36 rockets overnight in a "massive attack" on Ukraine, following reported strikes on energy infrastructure that resulted in power outages across the country.

And Japanese Prime Minister Fumio Kishida became the latest world leader to reproach Moscow for its talk of using nuclear weapons.

Kyiv's forces have been advancing along the west bank of the Dnipro river, towards the Kherson region's eponymous main city.

Kherson was the first major city to fall to Moscow's troops, and retaking it would be a major prize in Ukraine's counter-offensive.

In recent days, Russia has been moving residents in the region -- which Moscow claims to have annexed in September -- east to Russia, in efforts Kyiv has denounced as "deportations".

"Due to the tense situation on the front, the increased danger of mass shelling of the city and the threat of terrorist attacks, all civilians must immediately leave the city and cross to the left bank" of the Dnipro river, the region's pro-Russian authorities announced on social media.

A Moscow-installed official in Kherson, Kirill Stremousov, told Russian news agency Interfax on Saturday that around 25,000 people had made the crossing.

Sergiy Khlan, the Ukrainian deputy head of the Kherson region, said Russians were removing property and documents from banks and the passport office as they withdrew.

Ukraine's general staff said Moscow's forces had abandoned two more settlements in Kherson and were evacuating medical personnel from a third, accusing them of looting local civilians.

- A 'serious threat' -

Earlier Saturday, Japan's Kishida denounced Moscow's comments regarding the possible use of nuclear weapons in the Ukraine conflict.

"Russia's act of threatening the use of nuclear weapons is a serious threat to the peace and security of the international community and absolutely unacceptable," he said.

The 77-year period of no nuclear weapons use "must not be ended", said Kishida, speaking in Australia.

Since Russia invaded Ukraine in February, Putin has made several thinly veiled threats about his willingness to deploy tactical nuclear weapons.

Earlier this month, the European Union foreign policy chief Josep Borrell warned that the Russian army would be "annihilated" if Russia launched such an attack.

Washington has also warned Moscow of "catastrophic" consequences should they use such weapons.

Japan is the only country ever to have been hit with nuclear weapons: the US atomic bomb dropped on Hiroshima on August 6, 1945, which killed 140,000 people, and the second US bomb on Nagasaki, three days later, which killed 74,000 people.

- 'Afraid for our lives' -

At a train station in the town of Dzhankoy in the north of Crimea, a peninsula that Moscow annexed from Ukraine in 2014, Kherson residents were boarding a train for southern Russia, an AFP reporter saw Friday.

"We are leaving Kherson because heavy shelling started there, we are afraid for our lives," said Valentina Yelkina, a pensioner travelling with her daughter.

More than a million households in Ukraine have been left without electricity following Russian strikes on energy facilities across the country, the deputy head of the Ukrainian presidency Kyrylo Tymoshenko said on Saturday.

Fresh Russian strikes targeted energy infrastructure in Ukraine's west, the national operator said earlier, with officials in several regions of the war-scarred country reporting power outages as winter approaches.

Russians "carried out another missile attack on energy facilities of the main networks of Ukraine's western regions", Ukraine's energy operator Ukrenergo said on social media.

"These are vile strikes on critical objects," said Zelensky. "The world can and must stop this terror."

Power outages were reported in other parts of the country and local officials repeated calls to reduce energy use. Some parts of Ukraine have already cut their electricity use by up to 20 percent, according to Ukrenergo.

"Saturday in Ukraine starts with a barrage of Russian missiles aimed at critical civilian infrastructure," Ukraine's Foreign Minister Dmytro Kuleba said on Twitter. He once again urged Kyiv's allies to hasten the delivery of air defence systems.

Russia last week reported a "considerable increase" in Ukrainian fire into its territory, saying attacks had largely concentrated on Belgorod region and neighbouring regions of Bryansk and Kursk.

N.Fournier--BTB