Police are hunting two men - one said to be aged in his 20s or 30s, the other in his mid-40s - who allegedly attacked a third man with a sledgehammer at Stockton on Sunday.
Officers said a 38-year-old man was walking on Dunbar Street just before midnight when a car stopped near him.
As he approached the car, two men - one of whom was armed with a sledgehammer - approached. The 38-year-old attempted to flee but tripped and fell to the ground.
It was then, police said, the attackers hit the man in the head and legs with the sledgehammer before fleeing the scene.
The injured man was able to make his way home and was taken to hospital for treatment of a fractured skull, abrasions and bruising.
Police said on Monday that he remains in a stable conditions. A crime scene had been established in Dunbar Street.
One of the men police are searching for is described as being of Caucasian appearance, about 20 to 30 years old, with a thin build. The other man is described as being of Caucasian appearance, aged in his mid-40s with greying hair.
Investigations are ongoing.