Security camera footage captured two masked men climbing into the organization’s office in the town of Nazran and setting three rooms on fire. The attack came a week after the arrest of Oyub Tityev, the head of Memorial’s branch in Chechnya, on drug charges his supporters say are fabricated.

Unknown arsonists wearing masks torched the office of Russia’s renowned Memorial human rights group in the North Caucasus republic of Ingushetia on Wednesday morning.

“We see a clear link between this arson attack and the forces that are trying to destroy the work of Memorial’s human rights center in Chechnya and to force Memorial out of the entire North Caucasus region,” the group said in an online statement published Wednesday.

Memorial’s office in Nazran has reported on human rights violations in the region for more than 17 years.

The NGO said it considered the arson attack “an act of terrorism” and asked regional authorities to conduct an investigation.

The arson attack came three days after the arrival of a group of activists, lawyers and investigative journalists who were covering Titiyev’s case, the investigative Novaya Gazeta newspaper reported Wednesday.

“[The arson attack] is a clear signal to human rights defenders that should be interpreted as a threat,” the newspaper cited Titiyev’s attorney Pyotr Zaikin as saying.