"Proekt," an independent Moscow-based online news outlet which specialises in investigations, began to publish a series of articles in March looking into the role of a shadowy group of mercenaries known as Wagner.
Around the same time, Roman Badanin, its editor-in-chief, said his journalists began to get emailed threats promising physical retribution for their work.
Unknown individuals tried to break into his staff's personal accounts on Facebook, the Telegram messenger service and Google mail, he said, and one of his journalists was followed in the street by an unknown man who filmed her with a video camera.