Kolobnev left the Tour de France last week after testing positive for hydroclorotiazide following the fourth stage of the race.
"Since Alexandr Kolobnev's B sample came back positive, Team Katusha confirms the suspension of the rider," Katusha said in a statement.
"Kolobnev, formally, suspended himself," the statement added.
A decision on whether Kolobnev will be fired will be made after the Russian federation reviews the case, the team said.
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