TERRIFYING footage showing a boy bus-surfing before scaling an 18-storey building site and dangling from the top has been posted online.

The video, now on YouTube, shows the boy lying face down on the roof of a double-decker bus as it travels through Bournemouth town centre.

The boy’s hands are clearly visible in front of a Go-Pro as the bus travels around the Bath Hill roundabout and along Westover Road.

The footage then jumps to a building near the Lansdowne where viewers can see the boys climbing the stairs to the roof of the building.

One is seen balancing along a beam beside a sheer drop before swinging from a metal pole.

They then film themselves going back down the stairs before telling viewers they will post a new video every week.

They even show a “trailer” for the next episode.

Similar footage was posted in April when boys filmed themselves on top of the same building.

Just weeks before that a video had been posted of boys on top of a building in Holdenhurst Road.

Following the incident in April, security staff at the Holdenhurst Road building said they were doing all they could to stop people accessing the site.

One security worker said: “In the past, at other sites, we have caught them, but when they are turned over to police they are just let go.

“If they are never prosecuted, there is not much more we can do.”

Dorset Police Neighbourhood Inspector Jon Wasey said: “It should be nothing short of obvious that climbing onto the roof of any building or riding on the outside of a moving bus or other motor vehicle is an incredibly dangerous thing to do.

“Sadly, while such antics may be seen as amusing or thrill-seeking, they can end in tragedy. I would urge this activity to stop before somebody is seriously injured or killed.

“I would also encourage anyone with information about these types of incidents to please come forward to Dorset Police.”

Urbex, or urban exploring, is the practice of entering or climbing abandoned urban structures or buildings under construction.

The craze has grown in popularity on social media, where there have even been ‘tutorials’ posted on how to take part.

Police have warned that entering abandoned buildings or structures under construction could constitute illegal trespass.