MOSCOW – A day after protests swept by Russia in support of a jailed opposition leader, authorities said Monday that some participants face severe punishment, including protests in the prison system once known as the Gulag .
Kremlin spokesman Dmitry S. Peskov told a news conference on Monday that the protests “included a large number of hooligans and provocateurs” and that “the law must be applied with the utmost seriousness”.
For a second consecutive weekend, tens of thousands of people turned up in cities across Russia on Sunday to await the release of Alexei A. Navalny, the opposition leader, who was jailed for 30 days last month, after returning to Russia.
Mr. Navalny returned to his recovery in a German hospital after being poisoned in August with a military nerve agent, an attack confirmed by German, French and Swedish laboratories.
Mr. Navalny, 44, an anti-corruption activist who has been active in street protests in Russia for a decade, said the Kremlin was behind the poisoning and wanted to kill him. The Russian government has denied this and questioned whether Mr. Navalny is really poisoned.
According to the opposition leader, the almost fatal dose of poison, a sophisticated nerve agent called Novichok, was developed by the Soviet Union, in Mr. Navalny’s underwear posted, citing a confession from a Russian agent.
Mr Navalny returned to Russia, although authorities on arrival threatened to arrest him. He was then detained for violating the parole due to a conviction of financial crime in 2014 that the European Court of Human Rights ruled was politically motivated.
Mr. Navalny said the financial crime was devised by the Russian authorities and accusations of violating the parole were absurd as he could not report to a parole officer twice a month because he had been evacuated from Russia to Germany while in a coma. was after the attack on the nerve agent. .
He was arrested for thirty days for privileged detention. On Tuesday, a court will consider imposing a jail sentence that could put him behind bars for several years.
The prosecutor general’s office issued a statement on Monday stating that Mr. Navalny should be arrested for violating the parole, but all but to ensure that the outcome as judges only in a small number of cases in Russia’s criminal justice system defies the requests of the prosecutors.
Politics would indicate jail time for a shift in the government of President Vladimir V. Putin’s handling of Mr. Navalny. For years he was regularly sentenced to short-term imprisonment but never taken prisoner.
The imprisonment of political dissidents mostly ended in the immediate post-Soviet period, but was on a small and targeted scale under Mr. Putin revives.
After street protests in Moscow in 2012, the courts sentenced several dozen of the tens of thousands of protesters to long prison terms, apparently an example for others.
These few dozen cases were well publicized to highlight the illegality of street action, but the approach avoided inciting a large number of Moscow families to rage in a charge and venturing a spiral of oppression and protest. By contrast, police in neighboring Belarus have been holding at least hundreds of protesters against the government for long periods since last summer.
During Sunday’s rally, police detained 5,300 people across Russia, though many were released later that day.
It is unclear how wide the prosecutors will now throw. Several dozen cases have been reported that could lead to protests in the prison.
Mr. Peskov, the Kremlin spokesman, referred to people who behaved “more or less aggressively” towards the police when asking for severe punishments. “There can be no conversations with hooligans and provocateurs,” he said.
Supporters of Mr. Navalny said in a statement published online Monday that they expected prosecutors to justify riotous charges against protesters based on two incidents: a police car that caught fire and a man in an otherwise empty street who walked into a row of police running a club. Police have issued a statement saying they are investigating the car fire as vandalism.
The statement noted that the two episodes had been highlighted in the government media and that this could be a justification for the prosecution of participants in the riots against riots, which imposed long sentences. Short sentences in Russia are served in prison, while most are served longer sentences in penal colonies.