KYIV, UKRAINE -- More than 200 Russian and Ukrainian soldiers have returned home in a prisoner swap, the warring countries said Monday.

Russia's Defence Ministry said 106 Russian soldiers were released from Ukrainian custody as part of an agreement with Ukraine.

Andriy Yermak, Ukrainian President Volodymyr Zelenskyy's chief of staff, said that Russia freed 100 Ukrainian prisoners.

Neither announcement mentioned whether any intermediaries were involved in the agreement.

Some of the Ukrainian soldiers have severe injuries and illnesses, Yermak said in a statement published on Telegram.

He added that the latest of the sporadic prisoner swaps in the war that started in February 2022 was "not an easy one." He did not elaborate.

Ukraine's Co-ordination Headquarters for the Treatment of Prisoners of War alleged that almost half of the 80 men and 20 women soldiers who returned home "have serious injuries, illnesses or have been tortured." It presented no evidence for its claims.

According to Ukrainian news reports, one of the women prisoners is Valeriia Karpilenko, a border guard who had helped defend Mariupol's Azovstal steel plant. Last May, she married a Ukrainian soldier in the steel plant's basement while Russian forces surrounded the complex. Her husband was killed three days later.

The freed Russians were being flown on military transport planes to Moscow for medical treatment and rehabilitation, the Defence Ministry said.

Such exchanges represent one of the few areas of co-operation between Ukraine and Russia. The two sides have returned hundreds of each other's soldiers, as well as the bodies of fallen troops, since the war began.

Meanwhile, Ukraine's presidential office said at least six civilians were wounded in the latest Russian shelling.

Separately, Donetsk Gov. Pavlo Kyrylenko said Russian forces struck a power plant and residential buildings in the eastern province.

The Russians also shelled nine border villages in the provinces of Kharkiv, Sumy and Chernihiv.

Ukraine's Deputy Prime Minister Iryna Vereshchuk said in televised remarks that the country has nearly seven million internally displaced people, including about one million children.

Most of them have abandoned their homes in the east and the south to move to safer locations in central and western Ukraine.

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Associated Press Writer Yuras Karmanau in Tallinn, Estonia, contributed to this report