A firearms officer was taken to hospital after a dog bit his groin and thigh while he was chasing a "violent suspect" in west London.
Police were called to Bath Road in Hillingdon after reports of a fight involving people armed with knives and guns.
Armed police rushed to the Harlington area but the suspects had left. One man returned with a dog and was verbally aggressive towards officers.
The suspect was chased on foot and while running set his dog, a Belgian malinois, loose.
The canine, whose breed has been used by the US secret service to guard the White House, bit the officer in the thigh and groin area.
He was taken to hospital for stitches and is now recovering at home, while he remains off work. The incident happened shortly before midnight on November 22.
The suspect, a 33-year-old man, was initially arrested on suspicion of grievous bodily harm, common assault, affray and having a dangerous dog in public.
He was taken into custody and later bailed pending further enquiries. No further action will be taken with regards to the offence of grievous bodily harm.
The dog was seized and taken to a west London police station. It remains with police.
West area commander chief superintendent Pete Gardner said: “This incident is a stark reminder of the threat faced by police and I’d like to commend the bravery of this officer in dealing with a violent suspect and their dog.
“Our officers should be able to go about their lawful duty without the threat of violence and we will do everything we can to bring to justice any person who assaults or causes injury to a police officer.”
