Police detained over 5,400 people at demonstrations supporting him on Sunday.

MOSCOW — A Moscow court on Tuesday could order the imprisonment of opposition leader Alexey Navalny for up to three and a half years in what is widely seen as a test of whether the Kremlin is determined to remove him from the political scene following two weekends of large protests that have seen thousands detained.

Moscow’s city appeals court will rule on a request by Russia’s federal penitentiary service to change an old suspended jail sentence against Navalny into real prison time on the grounds he allegedly violated the terms of his parole.

The suspended sentence is from an embezzlement trial in 2014 against Navalny that was found by the European Court of Human Rights to be political.

Video posted by pro-Kremlin media on Tuesday showed Navalny being delivered to court in an armored prison van.

Navalny’s team has called on his supporters to protest outside the court and on Tuesday morning police had sealed off some streets around the building, deploying lines of helmeted riot police and putting up metal barriers.

Navalny’s wife Yulia — who was detained and released during the protests on Sunday — arrived for the hearing, walking through a scrum of media.

Navalny has been in detention since he was arrested upon landing in Moscow just over two weeks ago after returning to Russia for the first time since recovering from a nerve agent poisoning that has been linked to the Kremlin.

Since then, thousands of people have come out for two consecutive weekends to protest in support of him across dozens of cities across Russia, defying huge police deployments ordered to disperse them.

Police detained over 5,400 people on at the demonstrations nationwide on Sunday; the largest number of detentions during protests under the rule of president Vladimir Putin.

Tuesday’s court hearing could now see him imprisoned for years, something that until now the authorities have previously avoided and that would mark a dramatic turning point in the battle between Navalny and the Kremlin.

A decision to put Navalny behind bars for a lengthy period is likely to trigger further protests and fresh international condemnation from the United States and European countries that have already demanded Navalny’s release.

Despite Sunday’s protests, authorities have signaled they will press ahead with imprisoning Navalny and, on Monday, Russia’s prosecutor’s office said it supported the penitentiary service’s request that Navalny should serve real prison time.

The 2014 trial found Navalny guilty of embezzling money from the Russian branch of the cosmetics brand Yves Rocher, one of a series of legal cases brought by authorities over the years widely criticized by international rights groups as politically motivated.

Russian authorities have accused Navalny of failing to register for his parole while he was in Germany last year while he was incapacitated for a time and in a coma from the nerve agent poisoning.

The Kremlin has denied that Navalny’s detention is political or that is has any involvement in his poisoning.

Putin’s spokesman Dmitry Peskov on Monday defended the arrests during the protests saying police were acting harshly but appropriately and that some protesters had behaved violently.

“As for other people, I can repeat once again that a whole set of instruments is available to them to express their viewpoint lawfully, and any unlawful actions for these purposes are unacceptable,” Peskov told reporters.

Although he has been jailed for short periods many times over his activism and kept entangled in court cases for years, Navalny has never been imprisoned for an extended time. Many observers in Moscow believe because the Kremlin has not deemed it worth the political fallout and international criticism that would follow.

But after the alleged attempt to murder Navalny with the nerve agent poison, many observers now believe that calculus may have changed and the government believes it needs to remove him from the scene.

Navalny has built a grassroots following largely through his online investigations into alleged corruption by powerful Russians close to the Kremlin. After he was detained again, his team released a new film unveiling the staggering luxury of a secret palace allegedly built by Putin on the Black Sea.

The film has now been watched over 100 million times, forcing Putin to make a rare response denying it.

Pro-Kremlin media have since been allowed to tour the palace and a childhood friend and former judo sparring partner of Putin, the oligarch Arkady Rotenberg, over the weekend appeared in a report claiming he owned the building and intended to turn it into an apartment hotel.