Paramedics were threatened by thugs who went on to jump up and down on their ambulance after a vicious gang attack at a beauty spot.
Police have launched a major investigation after the 'shocking' incident.
The ambulance crew were treating a victim at the time after two men were attacked. One of the men was hit over the head with a stick and another was thrown to the ground after being grabbed by the neck.
Officers in Trafford are now appealing for anyone with information to come forward. Police patrols around Urmston Meadows, where the attack happened, are now expected to be increased over coming weeks.
GMP said an ambulance was initially called after a group of adults had spent the day at Urmston Meadows on Saturday when they were attacked at around 8pm.
A gang of between 10 to 15 youngsters aged between 13 and 16 were said by the force to have been involved.
Greater Manchester Police said: "The victims were about to leave when the group of young people attacked them.
"One victim was hit over the head with a stick and another was thrown to the ground after being grabbed by the neck.
"The offenders made off and an ambulance arrived to treat the victim.
"Whilst paramedics were treating the victim on Eeasbrook, the offenders returned continuing the attack, jumping on the ambulance and threatening paramedics."
No arrests have been revealed. It's not known how seriously anyone was hurt, but no major injuries were reported by the force.
Officers from GMP Trafford North reported the incident on their Facebook page.
Pc Conor Gallogly, the neighbourhood Officer for Urmston, urged anyone with information to come forward.
He said: "This shocking incident has occurred at what is a local beauty spot where local residents should be free to enjoy the good weather we've had recently.
"I would like to reassure the community that we are doing all we can to identify and purse any offenders and we will be increasing our presence in the area over the next few weeks.
"I would also urge anyone who has any information that could assist us in finding the people responsible to contact the police immediately."
Anyone who was on or around Urmston Meadows and Eeasbrook on Saturday who may have witnessed the incident should call 101 quoting incident number 3229-300520, or report anonymously via Crimestoppers on 0800 555 111.
