A French intelligence officer held hostage in Somalia since 2009 has reportedly been killed along with at least one other soldier during a botched rescue attempt by French troops.

The intelligence agency team flew into southern Somalia by helicopter under cover of darkness to try to free Denis Allex from the al Qaeda-linked Al Shabaab group.

French defence minister Jean-Yves Le Drian says there was "violent fighting" during the early-morning raid in the Horn of Africa country on Saturday.

He says 17 militants were killed in the raid, but he believes the hostage was also shot dead.

"Commandos broke into where Allex was being detained last night and immediately faced strong resistance," he told a news conference.

"Intense combat took place, during which - and now I speak with caution - everything leads us to believe that Denis Allex was unfortunately killed by his captors."

Sowing confusion, Al Shabaab issued a statement saying that Mr Allex was still alive and being held at a location far from the base where the French military helicopters attacked.

"Several French soldiers were killed in the battle and many more were injured before they fled from the scene of battle, leaving behind some military paraphernalia and even one of their comrades on the ground," the group said.

The insurgents also said they were holding an injured French soldier.

France says the raid was carried out by the DGSE intelligence agency that Mr Allex worked for.

"Faced with the intransigence of the terrorists, who refused to negotiate for three-and-a-half years and who were holding Denis Allex in inhumane conditions, an operation was planned and carried out," the defence ministry said.

Mr Allex was one of two French intelligence officers from the DGSE who were kidnapped by Al Shabaab in Mogadishu in July 2009.

One, Marc Aubriere, escaped a month later. Mr Allex had been held ever since in what Paris called "inhumane conditions".

The ministry says he was kidnapped while carrying out an aid mission with the Somali government.

France has previously said the two men were in the Somali capital to train local forces.

After his abduction Al Shabaab issued a series of demands, which included an end to French support for the Somali government and the withdrawal of African Union peacekeepers, whose 17,600-strong troops are helping battle the rebels.

A video of Mr Allex pleading with French president Francois Hollande to negotiate his release and save his life appeared on a website in October used by Islamist militant groups around the world. Reuters could not verify its authenticity.

Mr Hollande said at the time the government was seeking to start talks with any party able to facilitate Mr Allex's release.

Reuters