ST. PETERSBURG -- Masked state investigators raided the offices of the Memorial human rights group on Thursday and seized computers in what the group's staff said was a hunt for material deemed extremist.

Staff said the armed men removed computer hard drives and prevented them from leaving or making phone calls. They said police told them the search was linked to the publication of an article in a local newspaper defined as extremist by authorities.

Documents including a history of political repression in the Soviet Union and a computer-based tour of Stalin-era gulags were taken away, said staff member Yury Rybakov. "All these years of work are now in the hands of the investigators, and we do not know when and in what condition it will be returned," Rybakov said. "This is an act of repression against our organization."

An Investigative Committee spokesman told Interfax that the search was part of an investigation into a local newspaper article. He gave no details.