French hostage Philippe Verdon, who was kidnapped by Al-Qaeda in the Islamic Maghreb (AQIM) in Mali in 2011 and found dead several weeks ago, was executed with a shot to the head, prosecutors said on.
"After the return of the body to France, the autopsy... was able to establish that Philippe Verdon was murdered by being shot in the head," the Paris prosecutors' office said.
The body of Verdon, who suffered from an ulcer and tachycardia, an abnormally fast heartbeat, was flown back to Paris.
The possibility had previously been raised that he had died from his ailments and that his killing had been staged.
The 53-year-old was taken from a hotel in northeastern Mali in November 2011 by AQIM while on business, as was Serge Lazarevic, another French national.
His captors announced in March they had killed him in revenge for France's military intervention in the country.
But Paris had never confirmed this until his body was discovered in the country's north and identified this month.
French forces intervened in Mali in January to help the weak Malian military drive out Islamist rebels who had seized control of the country's north, angering extremists.
At least seven French citizens remain captive in Africa, with another two in Syria.