An 11-year-old British skateboarding prospect for the Tokyo Olympics is "lucky to be alive" after she suffered a harrowing crash in training.

Sky Brown vowed to "come back even stronger" from the accident that saw her airlifted to hospital with fractures to her skull and breaks to her left hand and wrist.

Brown had been training with Tony Hawk, a superstar of the sport, at his California base on Thursday.

Video footage of the lead-up to the crash was posted on the youngster's Instagram account, which is managed by her mother, Mieko, revealing the moment Brown seemingly attempts to cross from one ramp to another.

It showed her appearing to lose momentum and being unable to keep up with the skateboard, before she begins to fall as the footage is stopped.

She landed head-first on her hand. Emergency services and a helicopter are pictured in the video before the injured youngster is shown in her hospital bed.

Brown says to the camera: "I don't usually post my falls or talk about them because I want people to see the fun in what I do, but this was my worst fall.

"And I just wanted everyone to know that it's okay, don't worry, I'm okay. It's okay to fall sometimes and I'm just going to get back up and push even harder."

She added in a written note: "I’m excited to come back even stronger and even tougher."

Hawk responded to Brown's Instagram post by sending the message: "Worst day ever. Hope your surgery went well."

Brown's father Stu, quoted on the BBC, said: "Sky landed head-first off a ramp on her hand. When she first came to hospital, everyone was fearful for her life.

"Sky had the gnarliest fall she's ever had and is lucky to be alive."

Brown is hoping to become Britain's youngest Olympian at a summer Games next year.

Team GB sent her a message on Twitter, saying: "Get well soon, Sky Brown. We know you'll return stronger than ever."

Skateboard GB CEO James Hope-Gill said: "Our thoughts are with Sky and her family, and we wish her a speedy recovery."