Russian authorities on Tuesday raided the homes and offices of multiple human rights advocates and historians with the prominent rights group Memorial that won the Nobel Peace Prize last year.

The wave of searches, after which police took Memorial activists in for questioning, is part of a steady and sweeping crackdown that the Kremlin has unleashed against dissent in recent years. It has intensified after Moscow invaded Ukraine more than a year ago.

The group says the raids and the interrogations are connected to a criminal case that Russia’s Investigative Committee launched against the activists earlier this month.

The investigation was opened on the charges of rehabilitating Nazism, punishable by up to five years in prison.

Memorial runs a database of victims of political repressions, and among the names are three people who were convicted in Soviet times over collaboration with Nazi Germany. The group said that authorities are using those names on the list in their case against Memorial.

Oleg Orlov, the group’s co-chair whose apartment was among those searched, called the allegations “idiotic” in comments to reporters on Tuesday, before being hauled into a police precinct by a masked police officer in a bulletproof vest.

Memorial, one of the oldest and the most renowned Russian rights organizations, was awarded the 2022 Nobel Peace Prize along with imprisoned Belarusian activist Ales Bialiatski and the Ukrainian organization Center for Civil Liberties.

Memorial was founded in the Soviet Union in 1987 to ensure the victims of communist repression would be remembered. It has continued to compile information on human rights abuses and track the fate of political prisoners in Russia while facing a relentless crackdown from the Kremlin in recent years.

The group had been declared a “foreign agent,” a designation that brings additional government scrutiny and carries strong pejorative connotations, and over the years was ordered to pay massive fines for alleged violations of the ”foreign agent” law. Russia’s Supreme Court ordered it shut down in December 2021, a move that sparked outcry in Russia and abroad.

Tuesday’s raids come after Russian President Vladimir Putin called on the police to “harshly suppress any attempts of the adversaries and their agents on the territory of our country to rock our society.”

The action against Memorial elicited outrage among Russian opposition figures. Dmitry Gudkov, a Russian opposition politician in exile, called it “an act of intimidation.”

“You give them the Nobel Prize, we give them a criminal case,” Gudkov wrote on Facebook.

“Terror. The very terror, the memory of the victims of which is preserved by Memorial,” Gudkov said.