Russian troops have returned to Ukraine the bodies of dozens of Ukrainian soldiers killed at the Azovstal steel plant.

According to some world agencies, the bodies were allegedly transferred to the capital, Kyiv, where DNA analysis was being carried out to determine the identities of those killed, said Regiment Azov, one of Ukraine's units that ran the steel plant for almost three months before surrendered in May.

Ukraine on Saturday announced the first officially confirmed exchange of soldiers killed since the start of the war.

It was said that the two sides exchanged a total of 320 bodies, and the exchange took place on Thursday on the front line in the Zaporozhye region.

Anna Holovko, a spokeswoman for the Azov Regiment, said all 160 Ukrainian bodies handed over by the Russians were from the ruins of Azovstal.

She said at least 52 of those bodies were believed to be the remains of Azov Regiment soldiers, and Maxim Zorin, a former regiment commander who now heads the Kyiv-based military unit, confirmed that bodies from the steel plant had been exchanged. .

Ukrainian President Volodymyr Zelensky has said there may be more than 2.500 prisoners at the Azovstal steel plant in Mariupol who are now being held in the Donetsk and Luhansk regions of eastern Ukraine.

Zelensky also said that Russia's plans regarding the treatment of these prisoners are constantly change.

At the same time, Russian forces continued to fight for control of Severodonetsk, a city in eastern Ukraine that is key to Moscow's goal of ending its occupation of the Donbas industrial region.

Zelensky said Ukrainian forces were holding their ground in the city as fierce battles were fought in the streets and Russia was trying to deploy more forces in the area.

- This is the 103rd day, and the Ukrainian Donbass is standing. It stands firm, the Ukrainian president said in his overnight address to the nation.

Zelensky said Russian forces planned to occupy the southeastern city of Zaporozhye, home to more than 700.000 people, which could seriously weaken Ukraine's position and allow the Russian army to advance closer to the central part of the country.