The German government says it now has "unequivocal proof" that the Russian opposition leader Alexei Navalny was poisoned with a Novichok nerve agent.
Mr Navalny was airlifted to Berlin for treatment last month after falling ill during a flight in Siberia and he has been in a coma ever since.
German Chancellor Angela Merkel says the case raises serious questions that only the Russian government can answer.
Navalny's team says he was poisoned on President Vladimir Putin's orders, but the Kremlin denies the allegation. Lucy Taylor is our correspondent in Moscow.
She speaks to Susie Ferguson.
