Chechen police raided the office of human rights group Memorial on Friday for the third time this week in connection to the internationally condemned arrest of its director, the group said in a statement.
The North Caucasus republic ruled by strongman Ramzan Kadyrov arrested local Memorial director Oyub Titiyev last week on alleged drug possession charges that activists say are bogus.
"On the morning of January 19, employees of the Chechen police came to the Grozny Memorial office," Memorial's statement said.
According to the statement, the officials were looking for the group's Moscow representative Oleg Orlov.
At the time of the raid Orlov was in Ingushetia, where masked men set fire to the local Memorial office on Wednesday.
The group said the arson attack was linked to Titiyev's arrest in Chechnya and blamed it on "forces who are trying to destroy the work of Memorial in Chechnya and pressure the organisation as a whole in the North Caucasus".
Police had already carried out raids on January 16 and 18.
Titiyev, 60, was detained on January 9 by traffic police who claimed they found a package with a marijuana-like substance on him. He was transferred to a detention facility following the arrest.
According to a translation from Chechen to Russian by Radio Free Europe's North Caucasus website Kavkaz.Realii, Kadyrov called Titiyev a "drug addict" and said rights activists are people "without a kin, nation or religion" on local state television.
Memorial speaks about human rights violations in Russia and has specifically accused Kadyrov of heading a totalitarian regime that uses kidnapping and torture.
Last month the US Treasury hit the Chechen leader with financial sanctions under the 2012 Magnitsky Act, accusing him of personal involvement in repression, torture and extra-judicial killings.
Titiyev's case has sparked concern from the West and rights groups, with Human Rights Watch calling it "another attempt to fraudulently frame a critic on drug charges" in a region where prominent activists have been similarly accused in the past.