A police officer was attacked and bitten by two pit bull dogs during an operation to make an arrest, Scotland Yard said.
The 57-year-old police constable had about 15 bites to his chest, face and arms.
The incident happened shortly before noon on Tuesday in a garden in Sladedale Road, Plumstead, south east London, a Yard spokesman said.
Officers were seeking to make an arrest for non-payment of a £1,500 fine.
The constable was in the garden next door in case the suspect tried to make off.
He was attacked as the dogs jumped from the suspect's garden over the fence to reach him.
A specialist dog section was called to subdue the dogs but because of their violent behaviour armed officers were called and the dogs were destroyed, the spokesman said. The injured officer was taken to a south London hospital and has now been discharged but remains on sick leave.
A 55-year-old man was arrested for non-payment of the £1,500 fine, and was also arrested under the Dangerous Dogs Act and on suspicion of assault on a police officer. He is in custody at a south London police station.
He was also arrested on suspicion of assault causing grievous bodily harm in relation to an incident in 2008 where a woman was attacked by two large brown pit-bull type dogs on Roydene Road, Plumstead. She sustained significant injuries to her body from the attack.
Detective Inspector Bruce Galbraith, from Greenwich CID, said: "This was an extremely distressing experience for this officer who was violently attacked by these dogs. We would like to ask the public to come forward and let us know if there have been any other incidents with these dogs or any information that may assist us with our investigation."