Kremlin to UK on spy attack allegations - Show evidence or apologise

A sign with a coat of arms is seen on the wall of the consular section of Russia's embassy in London, Britain, March 16, 2018. REUTERS/Toby Melville

MOSCOW (Reuters) - The Kremlin said on Monday that London would either have to back up its assertions that Russia was behind the poisoning of a former spy and his daughter in Britain with evidence or apologise "sooner or later."

Britain has accused Russia of being responsible for the use of a Soviet-era nerve agent called Novichok which was used to poison Sergei Skripal and his daughter Yulia.