The Biden administration on Thursday imposed sanctions and visa restrictions on four Russian agents who were involved in the poisoning of Russian opposition leader Alexei Navalny in 2020.

Alexey Alexandrov, Konstantin Kudryavtsev, Ivan Osipov and Vladimir Panyaev were sanctioned under the Global Magnitsky Act “because they acted as agents or on behalf of a person in a matter related to extrajudicial killings, torture or other gross violations of internationally recognized human rights committed against individuals that seek to uncover illegal activity by officials of the Government of the Russian Federation,” according to the US Treasury Department. All four had already been sanctioned under a different authority in August 2021.

The State Department imposed visa sanctions on the four, preventing them and their family members from entering the United States.

“Today’s actions are a reminder that there are consequences for violating internationally recognized human rights. The United States will continue to use the authorities at our disposal to hold accountable those responsible for such extraordinary acts,” Secretary of State Anthony Blinken said in a statement Thursday.

In August 2020, Navalny collapsed on a flight from the Siberian city of Tomsk to Moscow after being poisoned with the nerve agent Novichok. He was flown to Berlin and treated in the German capital before returning to Russia in January 2021. He has been imprisoned there since then.