Washington DC - The US on Wednesday again accused Russia of taking Ukrainian children, some of whom were put up for adoption, after fresh media accounts detailed alleged abductions.

"This is despicable and appalling. These Ukrainian children belong with their families inside Ukraine," White House National Security Advisor Jake Sullivan said.

"Russia is waging a war not just against the Ukrainian military – but against the Ukrainian people."

An investigation by the Financial Times published Wednesday identified and located four Ukrainian children allegedly transferred to Russia and then offered for adoption on the website usynovite.

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The children are aged between 8 and 15 years old.

According to the report, the name of one child was changed to Russian, and no mention is made on the site of their Ukrainian origins.

Ukraine is demanding the return of nearly 20,000 minors it says have been illegally taken by Russia since the start of Moscow's invasion in 2022.

The International Criminal Court previously issued an arrest warrant for Russian President Vladimir Putin and his children's rights commissioner Maria Lvova-Belova over the allegations.

Ukrainian President Volodymyr Zelensky told AFP last month that he planned to make the return of children a top priority at this weekend's summit in Switzerland on ending the war.