Al Jazeera’s Hoda Abdel-Hamid, reporting from Izyum in north-eastern Kharkiv, said the city offers a gruesome picture reflecting the “real tool of this war”.

“Izyum is now a desolated city, completely destroyed … there is barely a building who has not at least been damaged and I am talking about civilian buildings,” Abdel-Hamid said.

“Certainly a place where you see the real tool of this war, a city that has been besieged, bitterly fought between the two sides, now firmly under the control of Ukrainian forces,” she added, noting though that while Ukrainian soldiers are back roaming the streets, there is barely any sign of life.

Her comment comes after Ukrainian authorities discovered more than 400 bodies in a mass grave, including some with signs of torture.

Ukraine mourns one of its leading ballet dancer who lost his life this week fighting on the frontline with a memorial service in the country’s National Opera.

Oleksandr Shapoval, who died under Russian mortar shelling, was commemorated by soldiers of his unit, honour guards and members of Kyiv’s artistic community who layed flowers on his coffin before it was wrapped in a blue and yellow Ukrainian flag.

Shapoval, 47, retired from a long dancing career at the National Opera last year and began teaching in Kyiv before joining a territorial guard to defend the capital after Russia’s invasion. He later volunteered to join the army and fought in eastern Ukraine’s Donetsk region, scene of some of the war’s most intense fighting.

“To lose a friend is always very hard. To me he was a friend, brother-in-arms. He was a very decent person. My soul is empty. To me he will forever be alive,” said Roman Turshyiev, who fought alongside Shapoval in the same unit.

US President Joe Biden says that Russian President Vladimir Putin would change the face of the war if he would consider the use of chemical or tactical nuclear weapons.

“Don’t. Don’t. Don’t. You will change the face of war unlike anything since World War II,” Biden said during a interview with CBS news.

He was also asked what would be the consequences if Putin crossed that line.

“You think I would tell you if I knew exactly what it would be? Of course, I’m not gonna tell you. It’ll be consequential,” the president said. “They’ll become more of a pariah in the world than they ever have been. And depending on the extent of what they do will determine what response would occur,” he added.

One person has been killed and two others were injured near the Russian city of Belgorod, not far from the border with Ukraine, the TASS news agency cited local authorities as saying.

Russia’s defence ministry said its forces had launched raids on Ukrainian positions in several parts of Ukraine, and accused Kyiv of carrying out shelling near the Zaporizhzhia nuclear power plant.

Russian forces conducted their strikes in the Kherson, Mykolaiv, Kharkiv and Donetsk regions, according to the ministry, which added that Ukrainian forces had carried out an unsuccessful offensive near Pravdyne in Kherson.

According to the ministry, two incidents of Ukrainian shelling were recorded near Zaporizhzhia, Europe’s biggest nuclear power plant.

A spokesperson for Ukraine’s foreign ministry denied that Ukrainian forces had carried out shelling near the facility.

The third vessel charted by the United Nations World Food Programme (WFP) has left Ukraine’s Chornomorsk Black Sea port with about 30,000 tonnes of wheat on board, Ukraine’s infrastructure ministry said.

“The vessel is headed for Ethiopia. According to UN estimates, Ethiopia is on the verge of a food crisis,” the ministry said in a statement.

It said that in partnership with the WFP, three ships loaded with more than 90,000 tonnes of wheat are on their way to Ethiopia and Yemen.

“We plan to export another 190,000 tonnes, which are currently being purchased by UN partners,” the ministry said, adding that besides the Ikaria Angel, another nine vessels have left Ukrainian ports on Saturday.

As Ukraine continues offensive operations in the northeast of the country, Russian forces have established a defensive line between the Oskil river and the town of Svatove, British military intelligence said.

“Russia likely sees maintaining control of this zone as important because it is transited by one of the few main resupply routes Russia still controls from the Belgorod region of Russia,” the defence ministry said in a regular Twitter update.

“Any substantial loss of territory in Luhansk will unambiguously undermine Russia’s strategy. Russia will likely attempt to conduct a stubborn defence of this area, but it is unclear whether Russia’s front line forces have sufficient reserves or adequate morale to withstand another concerted Ukrainian assault,” it said.

Ukraine’s Prime Minister Denys Shmyhal thanked the United States for its support after Ukraine received a further $1.5bn in international financial assistance.

“The state budget of Ukraine received a grant of $1.5bn. This is the last tranche of $4.5bn aid from the United States from @WorldBank Trust Fund,” Shmyhal tweeted.

He said the funds would be used to reimburse budget expenditure for pension payments and social assistance programmes.

The Washington-based Institute for the Study of War (ISW) said in its Saturday report that satellite imagery suggested Ukraine troops crossed over to the east bank of the Oskil river in the Kharkiv region, placing artillery there.

The river, which flows south from Russia into Ukraine, had been a natural break in the newly emerged front lines since Ukraine launched its push about a week ago.

“Russian forces are likely too weak to prevent further Ukrainian advances along the entire Oskil River if Ukrainian forces choose to resume offensive operations,” the institute said.