International condemnation is growing over the arrest of Russian opposition leader Alexei Navalny, when he flew into Moscow. Navalny spent the past five months in Germany after being poisoned in an attack he says was ordered by President Vladimir Putin. The U.S., the U.K. and the European Union are calling for his immediate release. Germany has described Navalny's arrest as incomprehensible, while Amnesty International accuses Russia of waging a 'relentless campaign' against him. So just how much of a challenge is Navalny to President Vladimir Putin? Presenter: Kim Vinell Guests Alexander Soloviev, member of the board of Open Russia, an opposition movement. Sam Greene, Director of the Russia Institute at King's College London. Vladimir Sotnikov, political scientist at the Russian Academy of Sciences. - Subscribe to our channel: aje.io/AJSubscribe - Follow us on Twitter: twitter.com/AJEnglish - Find us on Facebook: www.facebook.com/aljazeera - Check our website: www.aljazeera.com/ #AlJazeeraEnglish #InsideStory #Scotland #UK