One Direction's Niall Horan, Nicki Minaj and Rita Ora have paid tribute to celebrity photographer Matt Irwin following his unexpected death on Friday (06May16).

The British photographer was just 36 at the time of his passing. A cause of death has yet to be announced.

Niall was among the first of his famous friends to remember him by posting a photo of the pair on Instagram.com on Friday, with the touching caption, "Rest well Matt. Can't believe I'm (sic) writing this. Incredible person."

Harry Styles, who Matt snapped for the singer's birthday earlier this year (16), has yet to comment on the news of his death.

Nicki Minaj also took to Instagram to pay her respects to the "sweet" photographer.

"I just don't want to believe he's gone," she captioned an image of the pair smiling for the camera.

"He literally took my pics 3 months ago after I specifically REQUESTED him!!! (sic) Always made me so happy on set. Always so loving & sweet & optimistic. This is so surreal. He was just so unbelievably TALENTED!!!! God bless his family. Rest in peace my love. #RIPMattIrwin."

Rita Ora was another star to express her shock at his loss on social media, writing, "Matt Irwin, you were always smiling, I'm so lucky to off (sic) known you, and shooting so many fun things together. Rest in peace my friend, sending love and healing to the Irwin family. #RIPMatt".

British fashion designer, presenter and model Alexa Chung shared a photo of her pulling sad faces with Matt, too, and captioned the shot, "Sorry to hear you left so soon. Will break out the summer shorts in your honour."

Most recently, Matt worked with Years & Years, Miley Cyrus and Cara Delevingne.

He began capturing images when he was 15 after a friend gave him a camera, and frequently used Instagram to showcase the artists he had been working with.

Bosses at his photo agency CLM have made no comment on the report.