Terrified residents watched in horror as “swarms” of teenagers attacked two women – including one on a mobility scooter.
Police Scotland confirmed it is appealing for anyone who witnessed the incident to get in touch with officers.
The attacks took place on Millfield Road at the junction with Kirkton Road in Arbroath on Friday night.
One woman, who asked not to be named, said: “There were swarms of young people. I saw about 30 boys and girls. They were gathered round the young woman kicking and attacking her.
“It looked horrific. She was curled up screaming.
“Then an older woman went to her aid and they were giving her the most awful verbal abuse.
“I think the young woman had gone to ask the youths to not make so much noise because they were right next to a sheltered housing complex where there are a lot of disabled and ill people.”
Another resident said: “A woman went to ask a group of young people to quieten down.
“She seemed to be attacked then another woman on a mobility scooter who went to her aid was also given a really hard time by the group.”
A Police Scotland spokesman said: “An altercation took place which has resulted in separate complaints of assault being made, which are both being investigated.”