A new round of U.S. sanctions on Russia over the poisoning of a former spy in Britain last year has gone into effect on Monday.

Washington imposed an initial batch of sanctions last year on Russia after determining that Moscow had used a nerve agent against a former Russian double agent, Sergei Skripal, and his daughter Yulia, in Britain. The Kremlin has repeatedly denied claims that Russia’s GRU military intelligence agency poisoned the Skripals in Salisbury in March 2018.