Ukrainian Forces 'Holding On' In Key Donbas Battles

President Volodymyr Zelensky said Ukrainian forces were "holding on" in the flashpoint eastern city of Severodonetsk where intense street battles with Russian troops could determine the fate of the Donbas region.

Moscow has concentrated its firepower on the industrial city, which it now mostly controls, with the area's governor saying on Friday that Russian forces had destroyed a major sports arena.

Pro-Russian rebels sentenced one Moroccan and two British fighters to death on Thursday after they were captured while fighting for Ukraine and accused of acting as mercenaries for Kyiv.

Zelensky said in his evening address on Thursday that several "cities in Donbas, which the occupiers now consider key targets, are holding on".

He added that Ukrainian forces have made positive strides in the Zaporizhzhia and Kharkiv regions outside Donbas, and are in the process of "liberating our land".

With the fiercest fighting now concentrated in Severodonetsk, governor Sergiy Gaiday -- who earlier called for Western artillery to quickly help secure a Ukrainian victory -- said "one of the symbols of Severodonetsk was destroyed. The Ice Palace burned down."

People in the town of Lysychansk, which is located near Severodonetsk, spoke to AFP about the stark choices the war has forced on them: either stay and brave the shelling, or flee and abandon their homes.

Yevhen Zhyryada, 39, said the only way to access water is by heading to a water distribution site in the town.

"We have to go there under shelling, and under fire," he said. "This is how we survive."

But others have chosen to pack up their belongings and get as far away from the fighting as possible.

"Life made me leave. The constant shelling. And also my grandson. My grandson pleaded with me: 'Grandma, come to us.' Only it's not clear for me where to go, I left their address at home," Lyubov Akatyeva, 65, said.

Defence Minister Oleksiy Reznikov has said around 100 Ukrainian soldiers were being killed every day in frontline fighting and as many as 500 wounded.

Western countries have provided weapons and aid to Ukraine since the February 24 invasion, while some people from abroad have joined the fight against Russian forces.

Separatist authorities in the Donetsk region of the Donbas ordered the death penalty for Aiden Aslin, Shaun Pinner and Saadun Brahim, Russian media reported.

Britain's Foreign Secretary Liz Truss called the sentence "a sham judgment, with absolutely no legitimacy", while a spokesman for Prime Minister Boris Johnson said the sentence contravenes prisoner rights under the Geneva Convention.

Britons Aslin and Pinner surrendered in April and Brahim surrendered in March in the eastern town of Volnovakha.

During a trial that lasted three days, the men pleaded guilty to "actions aimed at seizing power and overthrowing the constitutional order of the Donetsk People's Republic", Russian news agency Interfax said.

A lawyer representing one of them told the TASS news agency that they would appeal.

Pro-Russian separatists have held part of the Donbas region since 2014 and it is now the focus of Moscow's offensive after its forces were repelled from Kyiv weeks into the invasion.

Russia has repeatedly warned the West against getting involved and said it had targeted a Ukrainian training centre for "foreign mercenaries" in the Zhytomyr region, west of Kyiv.

The Ukrainian presidency said four people were killed in a Russian air strike on Toshkivka, a village around 25 kilometres (16 miles) south of Severodonetsk.

It reported seven other deaths in fighting across the country.

In Kyiv, Ukraine's Interior Minister Denys Monastyrsky said the capital was in no immediate danger, but troops were keeping a line of defence all the same.

Russian President Vladimir Putin, meanwhile, appeared to compare his actions to Peter the Great's conquest of the Baltic coast during his 18th-century war against Sweden.

Zelensky on Thursday called for Russia to be expelled from the UN's Food and Agriculture Organization (FAO), blaming Moscow for "causing hunger" and spurring the global grain crisis by invading his country.

Ukraine's Black Sea ports export millions of tonnes of grain each year but have been blocked since the invasion, while Western sanctions on Russia have prevented Moscow from selling much of its grain abroad, sending food prices soaring.

The FAO warned that poor countries will suffer the most from the crisis as they were "paying more but receiving less food".

Moscow has also called for Ukraine to demine, but Kyiv has refused for fear of a Russian attack.