PARIS — Amid reports of continued skirmishes with Islamist extremists driven out of the main settlements of northern Mali, France renewed a promise on Wednesday that its soldiers would begin returning home within weeks, handing over authority to West African and Malian units charged with keeping the vast desert area under government control.

But French officials acknowledged that, despite their claimed military successes so far, new hostilities had erupted on Tuesday near the northern town of Gao between what were depicted as remnants of the insurgents and French and Malian forces, possibly foreshadowing a new phase in the conflict.

“From the moment our forces, supported by Malian forces, began missions and patrols around the towns which we have taken, we have encountered residual jihadist groups which fight,” Defense Minister Jean-Yves Le Drian said in a radio interview. He called the conflict a “real war.”

“We will seek them out,” he said, pledging to bring security to the recaptured areas. “Yesterday there was some rocket fire from residual jihadist groups in the Gao region,” he said, without going into detail.