France was investigating a claim by the North African offshoot of al-Qaeda that it killed French businessman Philippe Verdon who was kidnapped in Mali in November 2011, the Foreign Ministry said on Wednesday.

Al-Qaeda in the Islamic Maghreb (AQIM) said it killed Verdon on March 10, in retaliation for France’s military intervention against Islamist militants in the West African country, the Mauritanian news agency ANI reported.

Paris has told Verdon’s family to treat the report with caution, France Info radio reported.

Jean-Pierre Verdon told Agence France-Presse he was “very affected” by the AQIM announcement and that he had “no illusions” about the fate of his son, whilst still awaiting official confirmation of the news.

Verdon is one of 15 French hostages being held by radical Islamist factions in Africa, six of which are being held by AQIM.

The report of his killing comes as French and African troops continue their offensive against AQIM and two other jihadist groups in the mountains of northern Mali.

France launched an air and ground offensive two months ago to halt the rebels’ advance south towards the capital Bamako.

The fighting has since shifted from the northern towns that the rebels used to control — but subsequently lost — to the desert hinterland, where a total of seven hostages are believed to be being held.

Verdon was abducted in the northern town of Hombori, together with a colleague Serge Lazarevic. Their families said the two men were on a business trip related to a project for a cement factory.

Concern for the hostages had grown since the announcement in early March by Chadian forces fighting alongside the French in the Adrar des Ifogas mountains that they had killed two terrorist leaders, Abdelhamid Abou Zeid and Mokhtar Belmokhtar.

On Tuesday, Verdon’s father had complained about the lack of information coming from the combat zone.

“We’re in a complete fog and it’s unbearable,” he told RTL radio.

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