Police are hunting a man who tried to stab an officer during an attempted arrest in Berkshire.
An unnamed officer from Slough police station attended a domestic incident at Byron House, Langley, on Wednesday, and tried arrest a man.
The attacker then wielded an eight-inch knife and struck the officer on the back with the blade before making off in a black VW Golf.
The officer was "not seriously injured" in the incident, said police.
Ch Supt Brian Langston, of Thames Valley Police, said: "This illustrates the ever-present risk that our police officers face every day.
"Inquiries to locate the man are on-going."
The man is described as Somalian, about 5ft 6in tall and of medium build. He has black Afro-style hair, a goatee beard and moustache and was wearing a T-shirt and dark trousers.
He was last seen in Southall, London, on Wednesday afternoon.