MOSCOW/LONDON - Russia will soon expel British diplomats in retaliation for Britain's decision to kick out 23 Russian envoys over a chemical attack on a former Russian double agent, Foreign Minister Sergei Lavrov said on Thursday.In London, Foreign Secretary Boris Johnson ratcheted up the rhetoric against Russia, accusing it of glorying in the attack on Sergei Skripal, which he described as a way of scaring anyone who stood up to President Vladimir Putin.Britain says Russia is responsible for the poisoning with a Soviet-era 'Novichok' nerve agent of Skripal, 66, and his daughter Yulia, 33. They were found unconscious on March 4 in the city of Salisbury in southern England and remain critically ill in hospital.Moscow denies any involvement. The Kremlin said the British position was irresponsible and not backed up by evidence. It said Britain would not have to wait long for Russia's response.Lavrov was quoted by the official news agency RIA as saying the accusations were unacceptable and that British diplomats would be expelled.But in a series of British media interviews early on Thursday, Johnson said the evidence of Russian guilt was "overwhelming" because only Moscow had access to the poison used and a motive for harming Sergei Skripal."There is something in the kind of smug, sarcastic response that we've heard from the Russians that to me betokens their fundamental guilt," he told the BBC."They want to simultaneously deny it and yet at the same time to glory in it."Johnson said the attack was a way for Putin to send a message to anyone considering taking a stand against it that "You do that, you are going to die."