TIMBUKTU, Mali — French troops began to withdraw from Timbuktu on Thursday after securing the fabled city as they ramped up their mission in another northern Malian city, searching for Islamist extremists who may be mixing among the local population.
Colonel Thierry Burkhard, a French military spokesman, said Thursday that the operation to secure Gao is still under way, nearly two weeks after French and Malian troops moved into the area. New clashes nearby raised questions about how solid a hold the French military has on the strategic area.
There is a risk of ‘‘residual presence’’ of terrorists mixed among the population, Burkhard said from Paris. Extremists fired rocket launchers at French troops near Gao on Tuesday.
France launched a military operation in Mali on Jan. 11 to help the Malian government restore control.
Islamist extremists linked to Al Qaeda had imposed severe rule in northern Mali then started pushing toward the capital last month.
In a sign of heightened security, authorities briefly detained three Tuareg men in Gao on Thursday who were stopped after they did not have their identity papers.
The men, who came from a nearby village, were in Gao because they had missed their bus to a nearby market. The mayor intervened and the men were released.
Meanwhile, French troops began to draw out of Timbuktu, after greater successes in securing the desert city.
Soldiers in fatigues could be seen pushing an artillery cannon onto the barge crossing the Niger River, located on the southern perimeter of Timbuktu.
France has commandeered the river crossing, and on Thursday small convoys of military vehicles, including armored cars, trucks covered with camouflage-colored tarps, and vehicles loaded with supplies,were lining up, waiting for the barge.
While the population of Timbuktu worried that the departure of French troops will open the door for the Islamists to return, French military officials said they had fulfilled their mission here.
‘‘We have succeeded in handing over the majority of our responsibilities to the Malian Army and now she will assume our duties. But we will not leave the city of Timbuktu completely,’’ said Captain Franck, an official with the French operation codenamed Serval, after a sub-Saharan wildcat. He gave only his first name in keeping with military protocol.
He said some French forces will stay because ‘‘once we are gone, these people will come back in order to trouble the population. At the same time, we can’t stay indefinitely.’’
President Francois Hollande of France has withdrawal of 4,000 French troops could begin as early as March.
Foreign Minister Laurent Fabius reiterated that stance Thursday, saying the administration was sticking to its schedule and emphasizing the need for political as well as military action.
‘‘Our objective cannot be achieved with arms only,’’ Fabius said in an interview on French television BFM.