Champions Partizan Belgrade, aiming for a record third successive domestic double, kept up the pressure with a 2-1 win at Vojvodina Novi Sad.
Red Star displayed electronic banners in their Marakana stadium appealing to their fans for charity during a tepid performance in which they took a fortuitous lead from a controversial penalty.
Television replays showed Brazilian midfielder Cadu handled the ball and went down under minimal contact with a defender before he drilled in the spot kick.
Dejan Zivkovic swept home a close-range equaliser for the visitors on the hour before substitute Darko Lazovic headed a late winner for Red Star, who are battling the worst financial crisis in the club's history.
Sponsors have abandoned the 1991 European Cup winners and at one point last season, Red Star had their telephone lines and water supply cut off after their debts to creditors and players had soared to 30 million euros.
Partizan stretched their unbeaten run to 20 matches with Brazilian striker Cleo heading two first-half goals before Vojvodina pulled one back through Mario Djurovski.
Partizan host Vojvodina in next month's Cup semi-final and Red Star take on city rivals OFK for the other place in the final.
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