The Kremlin has denied that it killed the Russian opposition leader Alexei Navalny two years ago, using toxin from a type of South American dart frog. Navalny died suddenly while being held prisoner in a penal colony in Siberia. European countries including the UK have said Navalny was murdered using a poison developed from the highly poisonous frog. Scientists reached the conclusion after analysing samples from his body and identifying the poison, known as epibatidine. Western leaders said