LONDON - Britain banned all service sector exports to Russia on Wednesday and imposed sanctions on 63 individuals and organisations, its latest wave of measures to increase pressure on Moscow to reverse course and pull back from Ukraine.

Prime Minister Boris Johnson has been a leading supporter of Ukraine since Russia invaded on Feb. 24, framing London's sanctions against Moscow as a way of punishing President Vladimir Putin over a war the Russian leader describes as a "special operation" to denazify its neighbour.

The measures, the government said, would cut off Russia's access to Britain's management consulting, accounting and PR services, cementing a decision many had already taken for themselves, including the so-called Big Four accounting and consultancy firms -- Deloitte, EY, KPMG and PwC.

Many other services companies such as advertising groups have also sought to sell or close their Russian operations while some law firms have not taken on new clients.

"Doing business with Putin's regime is morally bankrupt and helps fund a war machine that is causing untold suffering across Ukraine," Foreign Secretary Liz Truss said in a statement.

"Cutting Russia's access to British services will put more pressure on the Kremlin and ultimately help ensure Putin fails in Ukraine."

Business Secretary Kwasi Kwarteng said Britain was "ratcheting up economic pressure on the Kremlin to change course".

Western countries have sanctioned dozens of individuals and companies in Russia since the invasion, often choreographed measures that Putin has said would only hurt the West because of higher food and energy prices.

Earlier, the European Union also took aim at accounting and PR services in proposals for its sixth and toughest round of sanctions against Russia.

Britain also imposed sanctions on individual journalists and media organisations.

"For too long RT and Sputnik have churned out dangerous nonsense dressed up as serious news to justify Putin's invasion of Ukraine," Tech and Digital Economy Minister Chris Philp said.

"These outlets have already been booted off the airwaves in Britain and we've barred anyone from doing business with them. Now we've moved to pull the plug on their websites, social media accounts and apps to further stop the spread of their lies."

(Reporting by William James and Elizabeth Piper; Editing by Kate Holton )