A security guard was killed in the early hours of Monday inside the Qatar Embassy in Paris, a source close to the investigation said.
The incident took place at around 0630 (0430 GMT), the source said, adding that the suspect had entered the embassy and had a row with the security guard, who died after being punched.
The Paris prosecutor's office confirmed the death and said one person had been arrested on the spot.
"I can confirm that an investigation was opened today on the count of murder," the prosecutor's office said.
