Two pitbull-type dogs have been shot dead by police after a man and a woman were bitten and another dog seriously injured.
Police were alerted that five dogs were dangerously out of control in Queen's Park in Chorley New Road, Bolton, at 10.20am on Sunday.
Emergency services found a woman in her 40s with her hand bitten and a man with injuries to both of his legs.
A second woman was also taken to hospital suffering from shock.
"Armed response officers were deployed to the scene and two dogs were humanely destroyed and two dogs have been seized," Greater Manchester Police said.
"Officers are currently searching the area for another dog who is believed to be part of the group."
This dog is described as large, short haired, of a bulky-muscular build and police warned it should not be approached.
A 38-year-old man was arrested on suspicion of affray and allowing a dog to be dangerously out of control in public.
"Highly trained officers responded quickly to the scene and took control to avoid the situation from escalating," said Superintendent Chris Allsop.
"The officers acted with our number one priority in mind - to protect people and prevent them from harm.
"I'd like to thank the public for their patience and full cooperation as we remain at the scene and carry out our inquiries."
Two roads that were closed have now reopened, and officers are trying to find the injured dog.
Anyone who sees a dog loose in the area is asked to tell police, while witnesses or those with information are urged to call police on 101 or Crimestoppers on 0800 555 111.