Police came under attack from a crowd of youths in Lurgan town centre on Saturday night.
It is estimated that up to 150 young people – some as young as 13 years of age – were involved.
Police say the troubled followed them having moved young people on from the subway area on the Portadown Road.
Stones and bottles were thrown from within the crowd.
The disorder continued in residential areas in the Shankill estate, where PSNI say residents had been tormented for a while.
Police – who struggled to contain the situation – appealed to parents via social media to know where their children are.
They said: “With those numbers, we will never have the resources to arrest as many as we’d like, but think about this one: if your child is out tonight and you don’t know where they are or what they’re up to, you could well be one of several who gets a follow up knock on the door from us.
“It could be words of advice, it could be being reported to the courts, it could even be arrest.
“If you don’t know where they are or what they’re at, time to fix that. Some of those out there are 13, maybe even younger.
“Out of sight should never mean out of mind.”