The killing of a guard at the Qatar Embassy in Paris in the early hours of Monday was a "heinous and unjustified" crime, the Embassy said, as French prosecutors opened an investigation, Reuters reports.
The incident did not appear to have any links to terrorism, a source close to the probe 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.
"An investigation was opened today on the count of murder," the prosecutor's office said.
The Paris prosecutor's office confirmed the death, and said one person had been arrested at the site.
"We await the result of the investigation and ask for the private life of the deceased's family to be respected," the Embassy said on Twitter.