Things just took an ugly turn in Justin Bieber’s feud with ex-girlfriend Selena Gomez. The pair, who split in 2014 after dating on and off for years, has been bashing each other on social media since Sunday.

According to Us Weekly, Bieber and Gomez’s back-and-forth banter got even nastier when the “Sorry” singer reportedly accused Gomez of cheating on him with former One Direction singer Zayn Malik. In the Instagram comments on one of Bieber’s posts, Gomez slammed the 22-year-old pop star for being unfaithful during their relationship.

“Funny how the ones that cheated multiple times, are pointing the finger at the ones that were forgiving and supportive, no wonder fans are mad. Sad. All love,” she wrote. Bieber reportedly fired back claiming the “Hands To Myself” singer was also unfaithful during their time together. “I cheated.. oh I forgot about You and Zayn?” he posted. Us Weekly wrote that fans spotted Bieber’s comment, took a screen shot and shared it on social media. However, some fans aren’t sure if the pop star actually wrote the remark about Gomez or if it was photoshopped. So far, Bieber’s post has over 548,000 comments.

Last month, Gomez opened up about rumors she was dating Malik telling InStyleUK that if the “Pillowtalk” singer had asked her out, she would have been spotted hanging out with him in public. “Just kidding,” she said, adding: “But not kidding.”  

Bieber and Gomez’s war of words started after Bieber ranted on Instagram that he was going to make his account private because of negative comments people were leaving about his rumored new girlfriend Sofia Richie. “This is getting out of hand, if you guys are really fans you wouldn’t be so mean to people like that,” he wrote.

Apparently, Bieber’s rant rubbed Gomez the wrong way because she left a comment slamming Bieber for asking fans to be nicer when he keeps sharing pictures of him and Richie, 17. “If you can’t handle the hate then stop posting pictures of your girlfriend lol — it should be special between you two only,” she wrote, according to the Daily Beast. “Don’t be mad at your fans. They love you.”

Bieber started following Gomez again on the photo-sharing site in June following their November 2014 breakup.