(Cover) - EN Showbiz - Rihanna has lashed out in response to the controversy surrounding photos she posted of herself cutting up white powder on a man's head.

The singer caused a stir yesterday after the images were seen on her Instagram page. The photos showed the Umbrella star sitting on a man's shoulders at California's recent Coachella music festival. She is seen putting a powered substance on the guy's cranium. The image was accompanied by the caption, "Memories don't live like people do #coachella."

The photo was shared across several media sites including MTV.

The 24-year-old has hit back at the entertainment website, posting a crude comment on her Twitter account last night.

"@MTVUK = PATHETIC C**TZ," she wrote.

Fans had posted more than 1000 comments about the image. Followers questioned the singer about the substance.

"Is that weed or coke?," one wrote, while another saying "Priceless I love this girl."

It's not the first time she has been accused of taking illegal substance. The singer was pictured smoking what appeared to be marijuana on holiday in Hawaii earlier this year.

Rihanna posted a number of risqu snaps of herself at Coachella on her Twitter page over the weekend, including one of herself in a skimpy bikini. She took to the stage with Calvin Harris and called her best friend Katy Perry up for a hug. (C) Cover Media