Ukraine said Monday that its forces had been pushed back from the centre of key industrial city Severodonetsk, where President Volodymyr Zelensky described a fight for "literally every meter".

The cities of Severodonetsk and Lysychansk, which are separated by a river, have been targeted for weeks as the last areas still under Ukrainian control in the eastern Lugansk region.

Regional governor Sergiy Gaiday said Monday that Russian forces were "gathering more and more equipment" to "encircle" Severodonetsk, and that they had "pushed our troops from the centre and continue to destroy our city".

The Azot chemical plant, where hundreds of civilians have reportedly taken refuge was still being shelled, he said.

In Lysychansk, three civilians were killed by shelling, including a six-year-old boy, Gaiday said.

On Sunday, Zelensky said the latest fighting in Severodonetsk was "very fierce", adding that Russia was deploying undertrained troops and using its young men as "cannon fodder".

Russia's massed artillery in that region gave it a tenfold advantage, the commander-in-chief of the Ukrainian military Valeriy Zaluzhny said Sunday.

"Every meter of Ukrainian land there is covered in blood -- but not only ours, but also the occupier's."

The capture of Severodonetsk would open the road for Moscow to another major city, Kramatorsk, in their steps toward conquering the whole of Donbas, a mainly Russian-speaking region partly held by pro-Russian separatists since 2014.

'War crimes'

Amnesty International on Monday accused Russia of war crimes in Ukraine, saying that attacks on the northeastern city of Kharkiv -- many using banned cluster bombs -- had killed hundreds of civilians.

"The repeated bombardments of residential neighbourhoods in Kharkiv are indiscriminate attacks which killed and injured hundreds of civilians, and as such constitute war crimes," the rights group said in a report on Ukraine's second biggest city.

Away from the battlefield, World Trade Organization members gathered in Geneva Sunday, and at the top of the agenda was the issue of tackling global food security threatened by Russia's invasion of wheat-producing Ukraine.

Tensions ran high during a closed-door session, where several delegates took the floor to condemn Russia's war, including Kyiv's envoy who was met with a standing ovation, WTO spokesman Dan Pruzin told journalists.

Just before Russian Minister of Economic Development Maxim Reshetnikov spoke, around three dozen delegates "walked out", the spokesman said.

That came a day after the head of the European Commission promised Ukraine would receive a signal within a week on its bid to join the European Union.

EU leaders are expected to approve the bid at an upcoming summit, though with strict conditions attached.

In Brussels, demonstrators brandishing Ukrainian flags circled European Commission headquarters Sunday in a show of support.

Chortkiv strike

The war has prompted Finland and Sweden to give up decades of military non-alignment and seek to join the NATO alliance.

But Turkey is blocking their bids and NATO chief Jens Stoltenberg said Sunday the issue may not be resolved by an alliance summit later this month.

The United States and Europe have sent weapons and cash to help Ukraine blunt Russia's advance, alongside punishing Moscow with unprecedented economic sanctions.

Russian forces said Sunday they had struck a site in the town of Chortkiv in western Ukraine storing US- and EU-supplied weapons.

Russia's defence ministry said the strike destroyed a "large depot of anti-tank missile systems, portable air defence systems and shells provided to the Kyiv regime by the US and European countries".

The strike -- a rare attack by Russia in the relatively calm west of Ukraine -- left 22 people injured, regional governor Volodymyr Trush said.

Concerns eased Sunday over Ukraine's largest nuclear power plant in Zaporizhzhia. Captured months ago by Russian forces but still operated by Ukrainians, the station had ceased transmitting vital safeguards data two weeks ago.

But plant officials working with the International Atomic Energy Agency have succeeded in restoring transmission, the IAEA said.

Rafael Grossi, director general of the UN agency, said it still wanted to send inspectors to the plant "as soon as possible".

Sentences defended

Alongside the physical fighting, the war is being played out through the courts.

Pro-Moscow separatist authorities in the Donetsk region this week sentenced to death two Britons and a Moroccan for fighting with the Ukrainian army.

The sentences sparked outrage in Western countries, but separatist Donetsk leader Denis Pushilin said Sunday he would not alter them.

"They came to Ukraine to kill civilians for money," he told reporters, calling the punishment "perfectly fair".

The families of Britons Aiden Aslin and Shaun Pinner say they have been living in Ukraine since 2018.

Ukrainian courts have handed three Russian soldiers long prison sentences at war crimes trials.