TIMBUKTU, Mali — In a new phase of the Mali conflict, French airstrikes targeted the fuel depots and desert hideouts of Islamic extremists in northern Mali overnight Monday, as French forces planned to hand control of Timbuktu to the Malian army this week.

After taking control of the key cities of northern Mali, forcing the Islamic rebels to retreat into the desert, the French military intervention is turning away from the cities and targeting the fighters’ remote outposts to prevent them from being used as Saharan launch pads for international terrorism.

The French plan to leave the city of Timbuktu on Thursday, a spokeswoman for the armed forces in the city said Monday. French soldiers took the city last week after Islamic extremists withdrew. Now the French military said it intends to move out of Timbuktu to push farther northeast to the strategic city of Gao.

“The 600 soldiers currently based in Timbuktu will be heading toward Gao in order to pursue their mission,” said Capt. Nadia, the spokeswoman, who only provided her first name in keeping with French military protocol. She said that the force in Timbuktu will be replaced by a small contingent of French soldiers, although she declined to say when they would arrive.

On Monday, French troops in armored personnel carriers were still patrolling Timbuktu. In the city’s military camps, newly arrived Malian troops were holding meetings Monday to prepare to take over the security of the city once the French leave.