Kyiv (Ukraine) (AFP) - Pro-Russian authorities on Saturday urged residents in the southern Kherson region, which Moscow claims to have annexed, to leave the main city "immediately" in the face of Kyiv's advancing counter-offensive.
The call came 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.
Air defence 'highest priority'
In his evening address Saturday, Zelensky said Ukraine was working with international partners to extend sanctions to "all Russian propagandists, so-called 'opinion leaders' and show business representatives who support or justify terror".
Russian media workers and celebrities who had backed Russia's invasion "should receive a full package of individual sanctions so that they can't do anything around the world at all", he added.
Foreign Minister Dmytro Kuleba said that he had had his first call with Italy's newly appointed foreign minister Antonio Tajani.
Wishing him success, Kuleba stressed that Ukraine's "highest priority" was to "swiftly receive air defence systems".
Russian air strikes on energy facilities across the country have left more than a million households in Ukraine without electricity, the deputy head of the Ukrainian presidency Kyrylo Tymoshenko said earlier on Saturday.
Fresh strikes targeted energy infrastructure in Ukraine's west, Ukraine's energy operator Ukrenergo said on social media, and officials in several regions of the war-scarred country reported power outages.
"These are vile strikes on critical objects," Zelensky said earlier Saturday."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.
In the Russian Belgorod region bordering Ukraine, at least two civilians were killed in strikes on Saturday, according to the local governor Vyacheslav Gladkov.
Nearly 15,000 people were left without electricity, he added.
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.
