MOSCOW -- Russian opposition politician Aleksei Navalny arrived in Moscow from Germany, where he was being treated after being poisoned, and was promptly detained by law enforcement authorities at Moscow's Sheremetyevo airport.

A live broadcast of his arrival showed police taking the 44-year-old Kremlin critic away on January 17 at the passport control booth.

His lawyer, who was travelling with him, was not allowed to accompany him. His wife, Yulia Navalnaya, who was also on the flight, was allowed to pass through passport control.

The statement said Navalny would be held “until a court ruling” on the matter.

The move, which could see Navalny jailed for 3 1/2 years for allegedly flouting the terms of a suspended prison sentence, sparked an immediate wave of criticism of President Vladimir Putin from both inside and outside the country.

"Putin seems to be doing everything possible to make @navalny into a national hero. After poisoning Navalny, which required German doctors to save his life, Putin arrests him on return for parole violations because he was in Germany," tweeted William Browder, a U.S.-born British investor and the CEO and cofounder of Hermitage Capital Management, the investment adviser to the Hermitage Fund, which at one time was the largest foreign portfolio investor in Russia.

Shortly before he was detained, Navalny told journalists at Sheremetyevo he was “happy” to be back in Russia and that he was confident he would not be arrested.

Navalny arrived from Germany after being flown there for emergency medical care after being poisoned in Russia in August 2020.

Laboratory tests conducted in Germany, France, and Sweden have established that Navalny was poisoned with a nerve agent of the Soviet-style Novichok class, a conclusion confirmed by the international Organization for the Prohibition of Chemical Weapons.

INFOGRAPHIC: In And Out: All The Times Aleksei Navalny Has Been In Prison

Navalny has said President Vladimir Putin is directly responsible for the poisoning. The Kremlin has denied any involvement.

Belarusian opposition leader Svyatlana Tsikhanouskaya, who has been leading protests against strongman leader Alyaksandr Lukashenka since a disputed presidential election in August 2020, wrote on Twitter that Navalny’s detention was “a dangerous step to depriving Russia of political alternatives.”

“Belarus has seen the outcome of such treatment of political opponents,” she wrote. “This does not serve the interests of the Russian people and of the country.”

Meanwhile, European Union members Estonia, Latvia, and Lithuania immediately issued a joint statement calling for the “imposition of restrictive measures” against Russia over Navalny’s detention, which they called “completely unacceptable.”

Navalny had been scheduled to arrive at Moscow’s Vnukovo airport, where hundreds of his supporters had gathered amid a massive riot police presence.

At the last minute, however, authorities closed Vnukovo to incoming flights and diverted Navalny’s plane to Sheremetyevo airport on the other side of the capital.

Police detained numerous people who were waiting for Navalny's arrival at Vnukovo, including Lyubov Sobol, a lawyer for Navalny’s Anti-Corruption Foundation; Ruslan Shaveddinov, a project manager for the foundation; and Novaya gazeta journalist Vlad Dokshin. Other journalists were also reportedly among the detained.

Navalny returned to Russia despite the authorities' stated intention to arrest him and potentially jail him for years.

Late last month, the FSIN demanded Navalny return immediately from Germany or face jail in Russia for violating the terms of his suspended prison sentence.

Navalny denies all wrongdoing in that case and says that it, like several other criminal cases filed against him in recent years, is retribution for his anti-Kremlin political activity.

Amnesty International immediately issued a statement saying the organization considers Navalny a “prisoner of conscience” and calling for the Russian authorities to release him without conditions.

Amnesty also called for the release of the dozens of Navalny supporters who were detained earlier by police at the airport.

Opposition politician and former Yekaterinburg Mayor Yevgeny Roizman wrote on Twitter that he had spoken by telephone with Navalny’s parents and told him their son was “a worthy citizen of Russia, brave and respectable.”

Navalny and other members of his Anti-Corruption Foundation could also face separate criminal charges of embezzling donors' funds, an accusation they vehemently deny. That charge carries a prison term of up to 10 years.

Earlier on January 16, Germany demanded that Moscow carry out a full investigation into Navalny’s poisoning and sent to Russia the transcripts of interviews its authorities conducted with him.

With reporting by Reuters and TASS