A French intelligence officer held hostage in Somalia for three and a half years is believed to be dead after a failed rescue attempt.

Seen here in a video broadcast by al Qaeda-linked insurgents, Denis Allex was one of two intelligence officers captured in Mogadishu in July 2009.

The other man escaped a month later.

The defence minister said Allex and a French soldier are believed dead after "very violent combat" with Somali insurgents Friday night.

But the militants holding Allex said in a statement he was alive and far from the base that was raided.

The al-Shabaab group also said they were holding an injured French soldier.