Rybka, 24, failed a doping test following a league game against FC Karpaty on November 27 after UEFA representatives paid an unscheduled visit to Shakhtar's training camp a few days later, Shakhtar Donetsk general manager Sergei Palkin was quoted as saying by Segodnya online paper.
Rybka, capped once after making his international debut in a friendly against Estonia last year, was in contention to be selected in Ukraine's squad for Euro 2012 which the country will co-host in June.
"We have received a letter saying Rybka is suspended from competitions held under UEFA as the investigation is ongoing, Palkin said.
"It will be a disqualification, but at the moment we do not know for what period. UEFA rules presume a term from half a year to two years."
Palkin said Rybka had taken a diuretic to lose weight but had not consulted with the club's doctor before doing so.
Shakhtar have brought back their former reserve keeper Bohdan Shust from fellow Ukrainian Premier League side Illichevets Mariupol to cover for Rybka.
Rybka's positive test has been the second major blow to Shakhtar's hopes of retaining their Ukrainian league title in the past week
Their long-serving Romanian coach Mircea Lucescu broke seven ribs and suffered a concussion in a car crash in Bucharest last week.
