French commandoes have attacked a base of Islamist militants in Somalia, a Somali intelligence official said. Residents of the town said they heard explosions and gunfire.

The attack occurred in Bulomarer. The intelligence official, who insisted on anonymity because he was not allowed to discuss the case with the press, said it was apparently aimed at rescuing a foreign hostage.

A French security adviser was kidnapped by the militant Islamist group al-Shabab in 2009.

"We heard a series of explosions followed by gunfire just seconds after a helicopter flew over the town," Mohamed Ali, a resident of Bulomarer, said by phone.

"We don't know exactly what happened but the place was an al Shabab base and checkpoint."

France also began attacking Islamist militants in Mali this week.