Rangers chief executive Martin Bain was "astounded" by the action after UEFA opened a case against the club over their Europa League second leg against PSV Eindhoven.
The Scottish champions already face action over the first leg in Holland and Bain claimed they appeared to be the victims of a "concerted and deliberate campaign".
Rangers disclosed they had been reported on the basis of a report from the Football Against Racism in Europe organisation rather than the UEFA match delegate, who was from Northern Ireland.
Bain told the club website: "We are absolutely astounded by this latest development and will defend our club's position very, very vigorously.
"We are still in the process of preparing our submission on the away game and to be confronted with this now seems chaotic to say the least. We have never said that sectarian singing is not a problem but this now has all the hallmarks of a deliberate and targeted campaign against the club."