The 20-year-old popstar triggered the end of the couple's relationship after he became "affectionate" with the 23-year-old singer in a recording studio a few months ago.
A source told TMZ.com: "Calvin heard they were very affectionate - she would sit on his lap [and] he would rub her back."
The RIP hitmaker moved in with Calvin in Los Angeles, but he's now had her belongings removed from his home.
The source explained: "He's already had her things removed from his LA house ... he also produced a few songs for her, but now he won't allow their release."
However, Calvin, 30, took to his Twitter account on Friday night to announce that he and Rita, whom he began dating in May 2013, had separated "some time ago", but he wishes her "all the best" in the future.
Meanwhile, Calvin appears to be surrounding himself with his friends following the split as he was spotted dining with a group of pals - including Rosie Huntington-Whiteley - in West Hollywood on Thursday night.
- BangShowBiz
