"I'm a bit sad because I love him (Mbolhi) like a son but I know it's good for him," Slavia president Ventsislav Stefanov told Bulgarian Darik radio. "I know he'll be the best goalkeeper in Russia."
Stefanov refused to confirm the transfer fee, saying only that Slavia would get "several million dollars" for the 24-year-old who represented France at youth level.
Mbolhi, part of Algerian team at the 2010 World Cup finals in South Africa, joined CSKA Sofia on a three-and-a-half-month loan deal in August to bolster their squad for the Europa League.
The 24-year old keeper made his debut for Algeria in 28 May 2010 against Ireland. But he sparkled during the World Cup finals 2010 producing a heroic performance in Algeria’s scoreless draw against England.
Since then he became the starting keeper for the Desert Foxes.
He was linked with moves to English Premier League giants Manchester United and Newcastle but none of them was completed.