DOMINIC Raab has called on Russia to immediately release Kremlin critic and opposition leader Alexei Navalny, expressing alarm at the swift detention in Moscow of Vladimir Putin’s political opponent.

The 44-year-old was detained at an airport in the Russian capital on Sunday after spending five months in Germany recovering from nerve agent poisoning that he blames on the Russian President. Mr Putin has denied any involvement.

“It is appalling that Alexey Navalny, the victim of a despicable crime, has been detained by Russian authorities. He must be immediately released,” declared Mr Raab.

“Rather than persecuting Mr Navalny, Russia should explain how a chemical weapon came to be used on Russian soil,” he said on Twitter.

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Mr Navalny’s detention has been condemned by governments around the world with the European Union, Germany and the US all speaking out about the arrest.

Mike Pompeo, the outgoing US Secretary of State, said he was “deeply troubled” by Mr Navalny’s arrest, adding a veiled criticism of Mr Putin.

“Confident political leaders do not fear competing voices, nor see the need to commit violence against or wrongfully detain, political opponents,” he said.

Prior to Mr Navalny’s arrival at Moscow’s Sheremetyevo airport, Russia’s prisons service said he had violated parole terms from a suspended sentence on a 2014 embezzlement conviction.

Officials said he would be held in custody until a court rules on his case.

Labour’s Lisa Nandy was also outraged by Mr Navalny’s detention. “He was the victim of a cowardly chemical weapons attack. Mr Navalny has shown great courage in returning to his homeland.

“His detention is unjustifiable and an insult to the Russian people. He must be released immediately and his attackers brought to justice,” added the Shadow Foreign Secretary.

SNP defence spokesman Stewart McDonald was equally forceful in his condemnation of Mr Navalny’s arrest.

He tweeted: “Having failed to crush Navalny’s bravery with poison the Russian government will now try, and fail, by putting him in prison.

“The free world must stand in unison in calling for his release. Those who continue to shill for Putin’s various outlets must surely feel shame tonight.”

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Tom Tugendhat, the Conservative Chairman of the Commons Foreign Affairs Committee, claimed Russia’s justification of Mr Navalny’s arrest was “designed to deceive”.

He pointed out: “Navalny missed probation hearings because he was recovering after the same Putin officials who ordered his arrest tried to murder him.

“If he gets beaten up and there are marks on the weapons, they’ll charge him with damaging Government property,” added the backbencher.

His Tory colleague Tobias Ellwood, who chairs the Commons Defence Committee, called Mr Navalny’s decision to return to Russia “incredibly brave”, in a sentiment echoed by Johnny Mercer, the Veterans Minister.

“Poisoned by the FSB yet he chooses to return to Russia and has now been arrested. Incredibly brave stand by Navalny in the name of democracy as we head towards Russian parliamentary elections,” said Mr Ellwood.

Meanwhile, Labour backbencher Catherine West called for a co-ordinated response from the UK Government, the EU and the incoming Joe Biden administration in the US.