The pop stars are claimed by the New York Daily News to have planned to spend the new year with each other, but had a row while away on holiday together in Mexico.
Selena is claimed to have got upset by Biebs spending his time tweeting topless pictures of himself for fans instead of spending quality time with her.
She is claimed to have flown back to the US on December 30, leaving him alone there one day longer.
And she has added fuel to the fire by tweeting on New Year's Day: "New beginnings. Fresh start. I love you all :)"
The paper claims that the pair have not seen each other since their fight, so it is uncertain whether the split is permanent. They last parted company back in November.
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