Putin opponent Alexei Navalny detained after arriving in Russia

Russian opposition leader Alexei Navalny was detained Sunday after arriving on a flight at a Moscow airport.

Navalny, who is an opponent of Russian President Vladimir Putin, had been in Germany recuperating from a nerve agent attack, according to the Associated Press.

Videos from an airport near Moscow showed riot police pushing against demonstrators who gathered to greet Navalny, according to Russian media.

Russian prison officials released a statement on Thursday saying Navalny engaged in 'malicious violations' of a suspended 2014 prison sentence, according to the New York Times. 

"The Federal Penitentiary Service of Russia in Moscow is obliged to take all actions to detain the violator A.A. Navalny pending a court decision to replace the suspended sentence with a real one," the statement said, according to the outlet.