Local reports identified the victim as Hasan Timur and his fiancée as Ayşe Gül.
The incident began in the morning when Gül tried to wake Timur so the couple could attend an appointment for medical examinations required before their marriage.
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An argument broke out inside the flat and later escalated into a physical confrontation, the reports said.
Timur allegedly punched his fiancée during the altercation. Gül then took a knife from the kitchen and stabbed him before calling emergency services for help.
Paramedics took Timur to hospital, where he later died from his injuries.
Police detained Gül and opened an investigation into the circumstances surrounding the death.
During questioning, the 19-year-old reportedly told investigators that she had acted in self-defence and had not intended to kill her fiancé.
The couple had already begun preparing for their wedding and arranging details of the ceremony before the dispute ended in tragedy.
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