The home of Zakhar Sarapulov, who headed the Irkutsk headquarters of Navalny's network of regional campaign groups, was searched early on the morning of December 28 and Sarapulov was detained by Russia's Investigative Committee.

The same morning, the offices of the banned Navalny movement's Tomsk headquarters were raided and its former head, Kseniya Fadeyeva, was detained at her cottage and taken in for questioning.

In Saratov, regional coordinator Andrei Gorodetsky was also detained, according to Siberia.Realities of RFE/RL's Russian Service.

It is unclear if a reported raid carried out against a fourth Navalny associate, Vadim Ostanin, the Navalny campaign's former Barnaul office head, has resulted in his detention or charges.

Leonid Volkov, who is among several Navalny associates who have fled Russia this year amid pressure from the Russian authorities, described the situation as a "huge disaster" in a post on his Telegram channel on December 28.

Volkov wrote that both Sarapulov and Fadeyeva, a representative in the Tomsk city council, had earlier refused his advice for them to leave the country.

RFE/RL's Siberia.Realities reported that both detainees have been allowed access to lawyers, who were not allowed to reveal details of their clients' cases.

Fadeyeva is suspected of using her official position in relation to the organization of an extremist group, according to Tomsk's TV2 information agency, a charge punishable by up to two years in prison.

TV2 also reported that Fadeyeva is likely to be transferred to Moscow for interrogation and is also suspected of participation in a nonprofit organization that infringes on the personality and rights of citizens, which is also punishable by prison.

Sarapulov and Gorodetsky have also reportedly been detained on suspicion of using their official positions to create or participate in an extremist community.

Navalny's Anti-Corruption Foundation and his political movement were declared extremist organizations by the Russian authorities in June and disbanded.

In November, a criminal case was opened against the head of Team Navalny's Ufa regional office, Lilia Chanysheva, who was charged with the creation and management of an extremist community.

Chanysheva was ordered last week to remain in pretrial detention until April 9.

Navalny himself has been in prison since February after he was arrested the month prior upon returning to Russia from Germany, where he had been undergoing treatment for a near-fatal poisoning with a Novichok-type nerve agent that he says was ordered by Russian President Vladimir Putin.

The Kremlin has denied any role in Navalny's poisoning.

Several of the opposition leader and Kremlin critic's associates have been charged with establishing an extremist group. Many of his close associates, including lawyer Lyubov Sobol, have fled the country amid pressure from the Russian authorities.