A police officer is in hospital after being stabbed in the back in Portsmouth, Hampshire Police said.
He was attacked in Stamshaw Park, where he had been on patrol, and taken to hospital by air ambulance shortly after midday.
The officer's injuries are non-life-threatening and his relatives have been informed.
One person has been arrested and is currently in custody.
The exact circumstance and motive for the attack have not been revealed.
Detectives said they do not believe there is any risk to the wider community.
Portsmouth City Council said the park has been closed until further notice.
Stephen Morgan, the Labour MP for Portsmouth South said he had spoken to the district commander and had been reassured about the situation.
"Concerned to learn of stabbing of a police officer. Portsmouth’s police put their uniform on and stand in harm’s way to keep our communities safe," he tweeted.
The investigations are ongoing and the authorities have appealed for witnesses to come forward.
Anyone who saw what happened or has any information about the incident is requested to call 101, quoting 44190063033.
Additional reporting from agencies
