French warplanes on Monday pounded Islamist positions in the town of Douentza in central Mali on the fourth day of an offensive against jihadists occupying the north of the country.

"Planes repeatedly bombed the Islamists' headquarters in Douentza. It was destroyed but the Islamists were not there," said a resident on condition of anonymity.

A local businessman said the place bombed was at the southern entry to the town and was the headquarters of the Movement for Oneness and Jihad in West Africa (MUJAO), one of the Islamist rebel groups occupying northern Mali.

"All the Islamists fled the town today (Monday)," he said.

A regional security source confirmed the fresh airstrikes, saying they also continued "in other areas" of the north.

On Sunday, strikes were carried out near the town, according to witnesses as the French also pounded insurgent strongholds in the key cities of Gao and Kidal.

France, working alongside the Malian army, on Friday launched the operation as the Islamists threatened to advance on Bamako, after months of hesitation over an African intervention force to help drive out the extremists.