Ukrainian President Volodymyr Zelensky said Thursday his country had not received enough help from the United Nations and Red Cross in bringing back Ukrainians, including children, held in Russia.
Kyiv says Russia is holding thousands of its civilians in captivity, including politicians and journalists who were detained by Russian forces after they launched their invasion in February 2022.
"Do we currently receive much assistance from organisations such as the UN or the International Committee of the Red Cross in protecting and securing the return of Ukrainian prisoners held in Russia? In fact, we do not," Zelensky said at a human rights conference in Kyiv.
"We all see, in particular, how weak the world's response is to what Russia is doing to Ukrainian prisoners," he said.
He said at least six mayors and community leaders were being held captive by Russia.
The mayor of the southern Ukrainian town of Dniprorudne, Yevgen Matveyev, died in Russian captivity after he was taken prisoner in March 2022, officials confirmed this week.
In October, Kyiv said Ukrainian journalist Victoria Roshchyna, who was captured while reporting from occupied east Ukraine, had also died in Russian detention.
Thousands of children in Moscow-held areas of east Ukraine have also been forcibly taken into Russia, in what Kyiv says is a war crime.
In March 2023, the International Criminal Court launched an arrest warrant against Russian President Vladimir Putin and his children's rights commissioner Maria Lvova-Belova on allegations of illegally deporting Ukrainian children.