WASHINGTON (AP) — The U.S. has imposed sanctions and visa restrictions on five Russian officials and an expert witness involved in the incarceration of Vladimir Kara-Murza, a Russian opposition leader who has been imprisoned in Moscow since April for speaking out against Russia's invasion of Ukraine.

He faces more than 30 years in prison.

Treasury sanctioned Elena Lenskaya, a Moscow judge; Andrei Zadachin, a special investigator; and Danila Mikheev, an expert witness for the Russian government on the case against Kara-Murza.

Governments and human rights organizations around the world, including the head of the United Nations High Commissioner for Human Rights, have called for Kara-Murza's release.

Friday's actions block the sanctioned Russians' access to U.S. bank accounts and other financial institutions. The U.S. State Department also imposed visa restrictions on Lenskaya, Zadachin and Mikheev.

Additionally, the State Department imposed visa restrictions on Deputy Justice Minister Oleg Sviridenko and two judges, Diana Mishchenko and Ilya Kozlov, who were involved in Kara-Murza's detention.

Kara-Murza was arrested after giving a speech in March 2022 before the Arizona House of Representatives, where he spoke out against the war. Since then, the Russian government has brought two additional criminal charges against him, for involvement in an "undesirable" foreign organization and for high treason.

"The U.S. Treasury joins our many national and international partners in calling for Vladimir Kara-Murza's immediate and unconditional release," said Treasury Under Secretary Brian Nelson.

"His arbitrary detention is another instance of the Kremlin manipulating Russia's legal system to silence dissent," Nelson said. "Kara-Murza, Alexei Navalny, and so many others in Russia who are unjustly imprisoned are not forgotten, and we will continue to promote accountability for perpetrators of these abuses on the international stage."

Last week at the Council on Foreign Relations, Treasury Deputy Secretary Wally Adeyemo said that as the invasion enters its second year, the U.S. will intensify its efforts to boost sanctions, including cracking down on sanctions evasion and putting economic pressure on countries, firms and people that continue to support Russian President Vladimir Putin's efforts to advance the war.