Rita Ora is reportedly "pretty cut up" over her split from DJ Calvin Harris.

The Radioactive singer started dating Calvin in May last year but it was reported yesterday that the couple had broken up.

Now a source close to the 23-year-old star has revealed the reason behind their split.

"The rows escalated over New Year and Rita ended up sharing a room with a friend," the source told British newspaper The Sun.

"Things changed between them and after New Year's Eve in Vegas, Rita was telling friends that she was single again. She is pretty cut up about everything but is throwing herself into work," the source added.

Rita had reportedly surprised Calvin by flying over to see him ahead of his December gigs in Puerto Rico.

But when they reunited, tensions mounted between the couple

Rita has since unfollowed Calvin on Instagram but has continued to put on a brave face and posted a series of selfies.

In the shots, Rita was shown relaxing by a pool and accompanying the pics she insisted she's feeling "excited."

She also managed to get a hair appointment after the split, before she jetted off to Vancouver where she is shooting the movie adaptation of Fifty Shades Of Grey.

The stars busy schedules have also been blamed as a reason for the split.

"It's been tough for both of them but it's been even harder for them to spend time together recently," another source told the newspaper.

"He's busy DJing and she's working on her new album and shooting 50 Shades Of Grey."