The 28-year-old woman was dragged through the streets of the northern town of Hameln by a rope behind a car, and sustained severe injuries. Her ex-partner later told police that he had committed the crime.
The woman, who had a rope tied around her neck, was dragged through several streets of Hameln, Lower Saxony on Sunday evening, local media report.
Witnesses found the woman, who has German nationality and is of Kurdish origin, lying abandoned in the street after the knot in the cord had apparently come loose.
She was rushed to a nearby hospital and remained in a coma in the city of Hanover after being transferred for specialized medical care.
Police spokesman Jens Peterson told local media on Monday that the woman's condition remained "very bad."
A 38-year-old man showed up at a police station in the town shortly after the incident and claimed he had committed the crime, Petersen added.
The man, who local media said was from a nearby town, was arrested. Prosecutors plan to charge him with attempted murder, local media said.
Police said the man's motive is still unclear, but are working on the assumption that the two people involved have a personal relationship. He is also German of Kurdish descent.
Local newspaper "Diester- und Weserzeitung" reported that the victim also had stab wounds, sustained before the car dragging incident.
Police have yet to confirm this account, and dismissed as "mere rumors" reports on social media that there had been a shooting in the town on Sunday evening which was linked to the crime.
mm/kl (AP, dpa)