Tinkov, whose digital credit card company, TCS Group Holding (TCSq.L), grew to become one of Russia's largest financial institutions, has been an outspoken critic of the war and president Vladimir Putin.Before he sold his stake, Britain imposed sanctions on Tinkov, saying he was "receiving benefits from the Russian government" through his stake in a systemically important company.Read more: Putin could use false claim of 'UK terror attack' to sabotage gas pipeline to UKIn an Instagram post published on Tuesday, he wrote: “I have decided to throw out Russian citizenship after Russia invades Ukraine, and start killing innocents there.Watch: UK warns Russia of ‘severe consequences’ for nuclear useThe tycoon was worth almost $10 billion (£8.7b) at his peak, and launched electronics, frozen food and beer brands before setting up Tinkoff Bank in the mid-2000s.Tinkov was forced to sell his 35% stake in TCS, Tinkoff Bank's parent, to Russian metals magnate Vladimir Potanin in April, following a string of anti-war comments."