Ukraine's president has made an impassioned plea to Western allies to speed arms deliveries and help stem "terrifying" casualties as Russian forces lay siege to the eastern city of Severodonetsk, destroying the last bridges into the industrial hub.

The cities of Severodonetsk and Lysychansk have been targeted for weeks as the last areas in the eastern Donbas region of Lugansk still under Ukrainian control.

Civilians were evacuated from the city of Sloviansk amid Russian bombardment of the eastern region
Civilians were evacuated from the city of Sloviansk amid Russian bombardment of the eastern region AFP / ARIS MESSINIS

President Volodymyr Zelensky said Monday the human cost of the battle for the region was "simply terrifying".

Zelensky expressed confidence in Ukraine's ability to reclaim territory, calling on the nation's allies to send more weapons.

"We just need enough weapons to ensure all of this. Our partners have them."

Fierce fighting continued in the eastern Donbas region
Fierce fighting continued in the eastern Donbas region AFP / ARIS MESSINIS

Presidential advisor Mikhaylo Podolyak on Monday listed items he said the Ukrainian army requires, including hundreds of howitzers, tanks and armoured vehicles.

"Being straightforward -- to end the war we need heavy weapons," he tweeted.

President Volodymyr Zelensky says Ukrainian forces are 'holding on' in the eastern Donbas region despite Moscow concentrating its firepower there
President Volodymyr Zelensky says Ukrainian forces are 'holding on' in the eastern Donbas region despite Moscow concentrating its firepower there AFP / ARIS MESSINIS

Regional governor Sergiy Gaiday said Monday that Ukraine's forces had been pushed back from Severodonetsk's centre after a weeks-long Russian offensive.

Russian President Vladimir Putin has compared his actions to Peter the Great's conquest of the Baltic coast during his 18th-century war against Sweden
Russian President Vladimir Putin has compared his actions to Peter the Great's conquest of the Baltic coast during his 18th-century war against Sweden SPUTNIK via AFP / Mikhail METZEL

"They destroyed all the bridges, and getting into the city is no longer possible. Evacuation is also not possible," he told Radio Free Europe.

He said Russian forces control 70 to 80 percent of the city but had not captured or encircled it.

Latest developments in Russia's war with Ukraine, with photos
Latest developments in Russia's war with Ukraine, with photos AFP / Sabrina BLANCHARD

Last week, Ukraine's defence minister said up to 100 of his troops were dying daily and 500 sustaining injuries. Previously, Zelensky had estimated 60-100 Ukrainian soldiers were dying daily.

With the screws tightening on the Lugansk region, Ukrainian forces have two choices: "to surrender or die", said Eduard Basurin, a representative for pro-Russian separatists.

The capture of Severodonetsk would open the road to Sloviansk and another major city, Kramatorsk, in Moscow's push to conquer Donbas, a mainly Russian-speaking region partly held by pro-Kremlin separatists since 2014.

The EU and the United States have strongly backed Ukraine
The EU and the United States have strongly backed Ukraine AFP / Yuriy Dyachyshyn

On Monday, Amnesty International 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.

In Brussels, demonstrators brandishing blue and yellow Ukraine flags circled the European Commission headquarters in a show of support
In Brussels, demonstrators brandishing blue and yellow Ukraine flags circled the European Commission headquarters in a show of support AFP / Kenzo TRIBOUILLARD

"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 about Ukraine's second-biggest city.

In Bucha, a town near Kyiv that has become synonymous with war crimes allegations, police said they had discovered another seven bodies in a grave.

"Several victims had their hands tied and knees bound," Kyiv regional police chief Andriy Nebytov said on Facebook.

A restaurant that launched Mcdonald's in Russia in 1990, heralding Moscow's opening up after decades of Soviet rule, reopened Sunday with a new name and logo
A restaurant that launched Mcdonald's in Russia in 1990, heralding Moscow's opening up after decades of Soviet rule, reopened Sunday with a new name and logo AFP / Kirill KUDRYAVTSEV

Dozens of bodies in civilian clothing were found in the town in April after Russian troops withdrew from the area following a month-long occupation.

Elsewhere in northern Ukraine on Monday, Russian rocket strikes hit the town of Pryluky, authorities said.

Pryluky, which lies about 150 kilometres (93 miles) east of the capital, is home to a military airfield.

In Donetsk, separatist authorities said three people were killed and four wounded in Ukrainian shelling on a market.

The nearby city of Lysychansk has been massively damaged after months of shelling, with no water, electricity or phone signal.

Ukrainian artillery uses the city's high ground to exchange fire with Russian forces fighting for control of Severodonetsk, just across the river.

Lysychansk resident Maksym Katerin buried his mother and stepfather in his garden Monday after a shell ripped through his yard, killing them instantly.

"I don't know who did this, but if I knew, I would tear off their arms," said Katerin.

Katerin's neighbour Yevgeniya Panicheva wept, saying Katerin's mother "was lying here, her stomach was ripped and her guts were falling out. She was a very good, kind and helpful woman. Why did they do this to her?"

"They bomb and they bomb and we don't know what to do."

A six-year-old boy was also killed in the city on Sunday, police told AFP.

Far from the battlefield, World Trade Organization members gathered in Geneva to address the threat to global food security since Russia's invasion.

Ukraine's deputy agriculture minister said on Monday that a quarter of his country's arable land had been lost but insisted national food security was not threatened.

"We planted really late because we needed to clear everything beforehand," including bombshells, Nadiia Ivanova, 42, told AFP.

The farm's warehouses currently hold 2,000 tonnes of last season's grain but there are no takers.