The U.S. on Thursday sanctioned four Russians they say were involved in the 2020 poisoning of Alexey Navalny, the country's most well-known opposition leader. The Treasury Department said the four individuals were members of Russia's Federal Security Service, or the FSB -- the main successor agency to the Soviet Union's KGB. "Today we remind Vladimir Putin and his regime that there are consequences not only for waging a brutal and unprovoked war against Ukraine, but also for violating the human rights of the Russian people," Brian Nelson, the under secretary of the Treasury for Terrorism and Financial Intelligence, said in a statement.