League champions Partizan were beaten 2-0 at Spartak Subotica and former European Cup winners Red Star suffered a 3-1 home defeat by last season's finalists Vojvodina Novi Sad, their fifth in a row against the northern Serbian side.
Red Star's former striker Andrija Kaludjerovic fired Vojvodina ahead thanks to good work by Enver Alivodic, who scored the second with a blistering shot before Petar Skuletic made it 3-0 on a freezing night in Belgrade.
The league's top-scorer Dragan Mrdja, in his second spell at Red Star, pulled one back in the closing stages but it was scant consolation for the home team's coach Slavisa Stojanovic.
"It's not a complete disaster but we must never again drag ourselves down to this level because we were second best in every department," Stojanovic told reporters.
Early goals by Dino Sarac and Aleksandar Noskovic gave Spartak sweet revenge against Partizan just four days after they were beaten by the champions 2-0 away in a league fixture.
"It's difficult to beat a side of Spartak's quality twice in only a few days but we were very poor today and having fallen two goals behind so early there was no way back," Partizan coach Vuk Rasovic told Arenasport television.
(Editing by Ed Osmond)
(Zoran.Milosavljevic@thomsonreuters.com)
