Shortly before seven o'clock pedestrians looked on in horror as flames leapt up from a woman who was sitting on a park bench at a playground, reports the Flensburger Tagesblatt.
Eye witnesses say that the woman didn't make a sound as the flames engulfed her.
Another reported to police that she saw two men in the vicinity shortly before the incident. They then made a quick getaway, the witness said.
The woman's life was saved when a quick-witted man took off his jacket and used it to beat down the flames.
Police and ambulance crews quickly arrived on the scene, and the woman, who originally comes from Mauritius and is in her mid-forties, was taken to the local hospital before being transferred to a specialist burns unit in Lübeck, but she is still in a critical condition.
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State prosecutors are keeping an open mind during investigations, although they currently believe the fire could have been a suicide attempt.