Russian security forces have raided the premises of opposition leader Alexei Navalny's Anti-Corruption Foundation, taking laptops and other equipment.
CCTV video posted online shows sparks flying as the door is forced open.
Mr Navalny linked the raid to his refusal to comply with a court order to delete a 2017 online film accusing Russia's prime minister of corruption.
The 43-year-old opposition leader says he was dragged out of the office, but he was not detained.
His foundation was declared a "foreign agent" by the Russian justice ministry in October, making it subject to more checks.
Thursday's raid came a day after Mr Navalny condemned the forcible conscription of one of his allies to serve at a military base in the Arctic.
What happened during the raid?
In a video recording made during the search in Moscow, he said officers from Russia's bailiffs service were seizing "everything".
CCTV footage shows the door of the foundation being cut open with power tools.
In another recording, officers wearing face masks are seen ordering staff against the wall.
Mr Navalny said the raid was connected to his 2017 documentary, which has been viewed 32 million times.
He has refused to remove the film, despite a court order. Mr Navalny has lost a libel case over the corruption allegations it made, and also faces criminal charges.
Opposition politician Lyubov Sobol, a Navalny ally, says this is the fourth raid on this office in the past six months.
In a statement, the Federal Bailiffs Service (FSSP) said investigations were "being carried out by the directorate of the FSSP in the Anti-Corruption Foundation as part of a criminal investigation".
Who is Navalny?
He has long been the most prominent face of domestic opposition to President Vladimir Putin.
He has accused Mr Putin's party of "sucking the blood out of Russia" and vowed to destroy the "feudal state" being built.
Mr Navalny has led nationwide protests but he has not been able to challenge Mr Putin at the ballot box.
His candidacy in the 2018 presidential election was banned over his conviction by a Russian court of embezzlement.
Mr Navalny denies the accusations and says his legal troubles are reprisals by the Kremlin for his vocal criticism.