NEW YORK • Now they have really got problems.

The rumoured bad blood between pop superstars Taylor Swift and Katy Perry spilled into the open on Wednesday, when Perry took to Twitter to take down Swift in a row set off by the nominations for the MTV Video Music Awards.

Rapper Nicki Minaj had on Tuesday voiced outrage that her video for Anaconda failed to be nominated for Video Of The Year. She suggested the music industry was biased against African-American women and preferred female stars "with very slim bodies".

One such slim star, Swift, who received nine and the most nominations for the awards, seemed to take Minaj's tweet personally.

"I've done nothing but love and support you. It's unlike you to pit women against each other. Maybe one of the men took your slot," tweeted Swift, who has cast herself as a feminist.

Perry, who commands Twitter's largest audience with 72.9 million followers, entered the fray a day later with pointed criticism of Swift, though she did not use her name.

"Finding it ironic to parade the 'pit women against other women' argument about as one unmeasurably capitalises on the takedown of a woman," Perry wrote.

She also wished R&B singer Rihanna had been nominated for her video for Bitch Better Have My Money, which came out on the last day of eligibility for the awards.

Swift was nominated for Video Of The Year for Bad Blood, which depicts her as an action hero.

Swift has said she wrote the song - with the lines "Now we got problems/And I don't think we can solve them" - about another pop star whom she accused of undercutting her by hiring people who had been working for her.

While Swift did not name the star, she was widely believed to be referring to Perry.

In the wake of the row, one of Minaj's fans pointed out the visual similarities between the videos for Bad Blood and K-pop group 2NE1's Come Back Home. But Joseph Kahn, who directed Bad Blood, responded on Twitter: "FYI: city, car, futuristic masks, body scanning. These are common sci-fi tropes."

AGENCE FRANCE-PRESSE