Featherston fire chief Colin McKenna also said children as young as 6 had been seen wandering the streets until 2am.
Mr McKenna said he had seen children trying to extort money from people in the town.
One victim, an elderly man, had been bailed up but the children fled when Mr McKenna and his partner approached.
The man told Mr McKenna he had been accosted twice by the children.
"As we walked back up the street we saw those kids trying to get another man to give them money," Mr McKenna said.
Another resident of more than 60 years said children two weeks ago smashed a window in his home and took a small amount of cash in daylight. He had told police.
One woman said the gang was attacking businesses, buildings and people in the town's central area, including the Fell Museum, skate park, the library and the Heritage Museum.
"They've lit fires in the skatepark, smashed a window at the Fell Museum and stole all the foam mattresses out of the St John's nearby," she said. "It's pretty bad - the kids are running wild and the police can't seem to handle them."
Mr Basher said police, CYF and South Wairarapa Safer Community Council, particularly its Life to the Max programme, were trying to resolve the problem.
"It all comes back to parental control. We are taking a holistic approach, looking at the families and into such things as whether these kids are getting three meals a day, have a bed to sleep in with clean sheets."