The Moscow office of the Open Russia civic movement established by exiled former tycoon Mikhail Khodorkovsky was searched by the police on August 9, the group has said.
The coordinator of Open Russia's human rights department, Polina Nemirovskaya said a large number of police officers entered the group's office in Moscow and searched the premises.
The Investigative Committee’s spokeswoman Svetlana Petrenko said the searches were linked to a longstanding case against Yukos, once Russia's largest oil company, founded by Khodorkovsky.
Yukos was dismantled after the 2003 arrest of Khodorkovsky, who was later convicted of financial crimes in two trials his supporters say were engineered by the Kremlin to thwart his funding of opposition parties, punish him for challenging President Vladimir Putin, and justify the transfer of his oil company's main production assets to state hands.
Khodorkovsky spent 10 years in prison and left Russia upon his release after being pardoned by Putin in 2013. He lives in Western Europe.
In April last year, the Russian Prosecutor-General's Office declared Open Russia "undesirable” and accused the NGO of conducting antigovernment activities.
Under a law signed by Putin in 2015 and widely criticized by rights groups, the government can brand foreign and international groups "undesirable organizations."
Rights watchdog Amnesty International has said Russian authorities are attempting to impose a full ban on the group.