Authorities in northwestern Russia have detained what they say are two branch leaders of the Jehovah’s Witnesses religious group, investigators said Wednesday.

They accused the unnamed 45-year-old and 67-year-old of “organizing extremist activity” in the form of religious services in the city of Vologda. Authorities placed the alleged leader of the Jehovah’s Witnesses’ Vologda branch in pre-trial detention and the older detainee under house arrest.

“The suspects actively organized illegal activities since January 2019, including religious performances and services, the distribution of extremist literature and the collection of funds under the guise of donations,” investigators said.

Russia banned the Jehovah’s Witnesses organization in 2017. 

The ban forced 395 Russian branches of the organization to shut down and at least 5,000 worshippers to flee the country, Time magazine reported last week.

Forty out of 280 Jehovah’s Witnesses awaiting trial in Russia have been placed in detention, the group says, while almost half are banned from leaving the country. At least 15 Jehovah’s Witnesses have been convicted

Danish citizen Dennis Christensen, the first Jehovah’s Witness to be convicted after the 2017 ban, and Russian nationals Sergei Klimov and Vladimir Alushkin are each serving six-year sentences.

Human rights groups have condemned the crackdown against the group as a violation of religious freedom. 

The United States has called on Russia to release the imprisoned Jehovah’s Witnesses and blacklisted two Siberian investigators on allegations that they tortured the believers in detention. The Kremlin said it planned an “adequate” response to the blacklists.

Jehovah’s Witnesses are a Christian denomination known for door-to-door preaching, close Bible study and rejection of military service and blood transfusions. 

The group estimates that it has about 170,000 followers in Russia.