Niall Horan has called out a fan for taking a picture of him as he slept on a plane.

The One Direction singer was lying down, covered with a blanket on a flight from London when he was snapped by the amateur plane paparazzo.

The 22-year-old tweeted "I think this shit is unreal. I mean if you can't sleep on a plane without people taking photos of you, what can u do."

The fan had originally posted the message "I sat directly next to Niall from One Direction for 9 hours on my flight home from London last night.

"He was sick and asked for no selfies, but here is a pic I snapped when he was sleeping lol he was so friendly... Not a British Duke... But an Irish popstar will do. Thanks for treating me so well Europe!"

I think this shit is unreal. I mean if you can't sleep on a plane without people taking photos of you,what can u do pic.twitter.com/3UvgLpHOcE

— Niall Horan (@NiallOfficial) August 2, 2016