Ukraine forces enter key Russia-annexed town, Zelensky vows to press onward

Map of Ukraine showing four regions where Moscow held contentious referendums from September 23-27 and annexed them

Local residents cross the Donets river next to a destroyed bridge

Ukraine said Saturday its forces had begun moving into the key eastern town of Lyman, located in one of the four Ukrainian regions that Russia annexed, with President Volodymyr Zelensky pledging more areas would follow within the week.

The latest development -- a feature of Kyiv's weeks-long counter-offensive against Moscow's invasion -- comes as Germany's defence minister made a surprise visit to Ukraine, but also amid accusations Russia killed 24 civilians in the eastern Kharkiv region.

Ukraine's defence ministry announced its forces were "entering" Lyman in the eastern Donetsk region after the army said it had "encircled" several thousand Russian troops near the town.

"Throughout this week, more Ukrainian flags have been raised in the Donbas," Zelensky said in his evening address. "There will be even more in a week."

With Russian losses mounting, experts have warned that President Vladimir Putin could turn to nuclear weapons to defend territory -- an option floated by a Putin ally.

"In my personal opinion, more drastic measures should be taken, up to the declaration of martial law in the border areas and use of low-yield nuclear weapons," Kadyrov said on his Telegram channel.

The developments came a day after Putin staged a grand Kremlin ceremony celebrating the annexation of the four Ukrainian territories.

The four territories create a crucial land corridor between Russia and the Crimean Peninsula, also annexed by Moscow, in 2014.

Elsewhere in the south Saturday, German Defence Minister Christine Lambrecht visited the port city of Odessa.

- Civilians gunned down -

Ukrainian troops on Friday had shown AFP reporters a group of vehicles riddled with bullet holes and several corpses in civilian clothes, a short distance east of the recently recaptured town of Kupiansk.

Kyiv also called for the immediate release of the chief of the Moscow-held Zaporizhzhia nuclear power plant, condemning his "illegal detention" by the Russians.

Zaporizhzhia -- Europe's largest nuclear energy facility -- has been at the centre of tensions with Moscow and Kyiv accusing each other of strikes on and near the plant, raising fears of an atomic disaster.

Following Friday's annexation, Washington announced "severe" new sanctions against Russian officials and the defence industry, and said G7 allies support imposing "costs" on any nation backing annexation.

He also vowed never to hold talks with Russia as long as Putin was in power.

Turkey said Saturday Russia's annexation was a "grave violation of the established principles of international law".

Kuleba also said Ukraine brought the annexations to the International Court of Justice and urged the Hague-based court to hear the case "as soon as possible".

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