The Human Rights Foundation told The Hollywood Reporter Hilary Swank had been warned about Kadyrov's alleged offenses before she attended the Oct. 5 event, along with her fellow film star Jean-Claude Van Damme.
Human Rights Watch urged the stars who showed up to return what they were paid to honor a man accused of overseeing law-enforcement and security agencies implicated in abductions, torture and executions in Chechnya.
"Ramzan Kadyrov is linked to a litany of horrific human-rights abuses. It's inappropriate for stars to get paid to party with him. It bolsters his image and legitimizes a brutal leader and his regime. And getting paid to be part of such a lavish show in Chechnya trivializes the suffering of countless victims of human-rights abuses there," Human Rights Watch said in a statement issued to The Hollywood Reporter.
Thor Halvorssen, president of Human Rights Foundation, described the celebrities' attendance at the party as "disheartening and shameful."
The Hollywood Reporter said Swank's and Van Damme's representatives did not respond to its requests for comment.