Ukraine's Center for Civil Liberties, the recipient of this year's Nobel Peace Prize, says it will seek justice for at least 680 Ukrainian civilian victims of Russian war crimes.

Members of the human rights organization held a news conference in the capital, Kyiv, on Friday.

The organization said the results of its survey show at least 686 civilians were detained and mistreated by Russian forces.

Of them, 265 were released, but 11 died and 410 remain in custody.

A woman who was detained in the northern province of Chernihiv in March and released last month attended the conference.

She spoke about having been forced to sing Russia's national anthem every day at a detention facility. She also said she witnessed the harassment of a Ukrainian woman whose hair was shaved off.

The center's executive director, Oleksandra Romantsova, said those illegally detained by Russia must be released unconditionally.

She said her organization will continue to seek justice for victims of Russian war crimes.