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Bullet wounds were found on his body which was discovered in the yard of an apartment block. Picture: Vg.ru
The 42 year old editor was known for his criticisms of the authorities in Minusinsk, a town with a 71,000 population some 440 kilometres (270 miles) south of regional capital Krasnoyarsk.
'The investigation is following various lines of enquiry regarding this killing, including that it may have been motivated by the victim's professional activities,' said a statement by investigators.
Bullet wounds were found on his body which was discovered in the yard of an apartment block.
While investigators are examining whether he was killed because of stories in his newspaper, other possible motives are also being examined.
Ton-M was founded by Popkov in 2014.
He earlier served on the Minusinsk city council before being stripped of his seat.
Archeologists discovered a new stone bracelet, two sharp pins, a marble ring and fox tooth pendants.