A man has died in hospital five days after he was allegedly bashed unconscious by a stranger on an inner Sydney street.

The man, 55, was walking along Crown Street in Darlinghurst on the morning of November 3.

He was near Kells Lane about 10.15am when he was approached by a 34-year-old man, police allege.

It is alleged the younger man kicked and punched the older man in the face in an unprovoked attack, which caused him to fall to the ground and lose consciousness.

The 55-year-old was discovered by a passerby, who believed from the man's serious injuries that he had been hit by a car.