Skater bashes ranger in shocking video

Graphic video showing a US skater bashing and spitting on a park ranger in Philadelphia on Friday is being investigated by authorities.

The video, shot on a mobile phone, was taken after the ranger told the teenager and his two friends that the couldn't skate in LOVE Park.

The skater punched the 35-year-old man in the face before wrestling him to the ground and kicking and stomping on his head and spitting on him. 

Witness Mariano Verrico, who recorded the incident on his phone, told NBC10 that the attack was unprovoked.

"Basically, [the ranger] was just doing his job. His voice wasn't raised, he wasn't cursing," he said.

"He never tried to fight with the kid. He never threw any type of punch at the kid or said anything negative."

"He got kicked in the head repeatedly and spit on," Verrico said. "When he was down towards the end..., the one kid who did everything leaned down and spit on him."

"It was really disgraceful," he said.

Verrico didn't want to intervene because he was "outsized", but he handed his video over to police for them to use in their investigation.

Skateboarding has been banned in the park since a 2002 renovation.