The hoodie-clad gang confronted terrified volunteers in Wheatley's Sandall Park last night - just days after a newly opened woodland adventure playground was set on fire - ahead of its official opening this weekend.
Members of the Friends of Sandall Park Group were checking the new wooden play structure - which was left damaged after ropes were set on fire earlier this week - when the gang descended on them.
Spokesman Sandra Crabtree, who was threatened, along with her husband Don, said: "We had gone down the park after getting calls that a lighter had been seen on the new play equipment.
"When we go there, we were surrounded by a hostile gang of around 15-20 youths who threatened Don.
"Had one struck out, I think we'd have got a right good kicking. It was a horrible experience, especially as it was pitch black and no-one could see us from the road."
The pair were surrounded and jostled by the gang who pulled their hoodies and balaclavas over their faces after being challenged by the pair who lead the group which has been instrumental in transforming the park over the last few years.
Added Sandra: "We saw several motorbikes blatting round the golf course and then the gang came over
"Their behaviour was totally threatening and they surrounded us. Some were on push bikes.
"One youth said they were going to come back and fire bomb the play equipment."
She added that the police were called via 999 and the Neighbourhood Response Team dispersed the gang.
Added Mrs Crabtree: "These are someone's sons and daughters - there were three girls and none of them were over 16.
"This was not a nice experience - but at least they know we're not going to stand for it. This is not good for the park or us, but there's no way we're letting them get away with it."
The same gang are thought to be responsible for damage to a massive new wooden climbing frame which is due for its official unveiling on Saturday.
Ropes on the new Woodland Adventure attraction at the park in Wheatley were burned and left charred after being targeted by the yobs. They have now been replaced.
Describing the incident on the group's Facebook page, Sandra wrote: "Whilst it's extremely annoying (to say the least) and while we'd like to just ask these numpties what they hope to achieve when it's been put there for everyone to enjoy - we will not give in.
"It took us three years, but we did get rid of the anti-social behaviour and and crime in the park some seven years ago.
"There's always going to be one or two numpties that want to try and spoil things for everyone, but we won't let them.
"This piece of equipment took us three years to get. It's not going to stop our plans to double it's size and give the decent kids the play area they want and deserve. We will pursue the offenders and hopefully - as always - the community the park serves will pull together and come up with some names."