The teenager fell from the roof of a flat on Richmond Place, Southsea, as he attempted to jump a 10 foot gap between two buildings.

He landed face first on to a flat-roof below.

Firefighters from Southsea station were first to the scene at 7pm to tend to the injured boy.

Ian Jefferys, green watch manager at the station, said: 'He had quite horrific injuries to his face and I think at least one broken limb. He was conscious though.

'Talking to his friend he was with, we understand this was some sort of free running stunt like you see on TV. I would like to strongly condemn this activity that they were doing.

'The lad tried to jump a gap between buildings. Obviously he didn't make it and fell about 30 foot, landing face first onto a flat-roof.'

Firefighters used a turntable ladder to gently lower the injured boy from the roof.

'We used the ladder with a spine board to get him down. With him landing on his face like that, there is always a danger of spinal injuries,' said firefighter Jefferys.

He added that the incident could have proved fatal: 'He was lucky to come away with what he has done considering the fall.'

A coastguard helicopter was due to land on Southsea Common to take the injured boy to Southampton General Hospital but it was decided it would be unsafe to make the landing and he was taken by road ambulance instead.

A spokeswoman for South Central Ambulance Service said the male suffered 'serious head injuries' from the fall.