An off-duty police officer was repeatedly stabbed in a “targeted attack” on a residential street in Essex, said police.
The officer suffered serious injuries to the stomach, chest and arm during the incident in Rayleigh on Wednesday night.
Witnesses told reporters the victim was attacked after someone knocked on his front door.
He remains in hospital in a serious but stable condition.
A man was arrested at the scene on suspicion of attempted murder.
“We believe this attack was targeted and that the officer and the suspect are known to each other,” he said.
“Our officer is in a stable condition in hospital and we are hopeful will make a full recovery.”
The attack took place in Church Road at around 9.10pm.
Steve Taylor, chairman of Essex Police Federation, said: “Last night, one of our colleagues was the victim of a horrendous, targeted and violent attack.
“He remains in hospital in a serious but stable condition.
“The thoughts of Essex Police Federation and the officers we represent are with our colleague and his family.
“The Force and Federation are supporting them and we would ask the media to respect their privacy.”
Rayleigh and Wickford MP Mark Francois described the attack as “an appalling crime”.
“My thoughts are with the officer concerned and his family,” he said. “Mercifully, while his injuries are serious, I have been told they are no longer life-threatening.
“Nevertheless, attacking a police officer on their own doorstep is absolutely wicked.”
Additional reporting by Press Association