Fireworks were thrown at a blind woman and her guide dog in a “shameful” attack.
A gang of three or four youths was stood about 65ft (20m) from the victim, who is in her 50s, when the explosives were thrown.
Despite not being hit, she was left very distressed and her startled dog fled the scene in Hyde Park, Leeds, West Yorkshire Police said.
The force said it was keen to speak to two women who came to victim’s aid.
It has appealed for witnesses to the attack, on Moorland Road, near Woodhouse Moor, at about 20:00 GMT on Tuesday.
On Twitter, police said those involved should be “utterly ashamed” and “To the 2 good Samaritans that came to her aid, you should be proud.”
Officers are also checking CCTV in the area.