The teenager accused of being the global mastermind behind the Blue Whale suicide group craze has been arrested.
Officers have detained the 17-year-old, who is accused of being the brains behind the death group, which has incited dozens of vulnerable children to take their own lives.
The unnamed Russian teenager issued threats to her victims to murder them or their family members if they failed to obey orders to complete tasks she set them involving cutting themselves with razor blades and other acts of self-harm.
A 21-year-old man has also been arrested near Moscow and accused on inciting adolescent girls to take their own lives.
The female "death group administrator" used threats against parents or siblings of her victims as added pressure on them to obey her and commit suicide, say Russian state investigators.
She also threatened the victims with being murdered in a sinister new twist to such online groups which pose rising concerns to police in many countries.
"This administrator was sending particular tasks - often life-threatening - to each of several dozen members of the group," said Colonel Irina Volk, of the Russian Interior Ministry.
"In contrast to similar groups, teenagers in this group were blackmailed with death threats against them or their relatives for not completing the tasks."
She set victims 50 tasks - in as many days - aimed at "creating psychologically traumatising situations", with the final stage demanding that the victim commits suicide.
The "brainwashing" by such social media groups often ranges from watching horror movies to waking in the middle of the night, and self harming.
The suspect - who cannot be named because she is underage - told alleged victims she "was a man".
She is shown barefoot in a police video as police examine books and drawings in her flat, many linked to suicide.