As the fight to drive out or capture the islamic militants from Mali continues, France reports fierce fighting in the mountainous region of northern Mali.

France’s Defense Minister, jean-Yves Le Drian announced on Tuesday that the fighting near the Algerian border with Mali is where the most difficult operations remains. This is where the “most radical terrorist groups” have fled the French onslaught.

The French estimate that the operations that have been going on in the African country since January 11th, have costed $133 million thus far.

Although the French government intends to wind down their efforts and hand the military operations over to the Malian army and the emerging African Force, Le Drian said that it is too soon to be speaking of withdrawal saying that French forces “are now at the heart of the conflict.” There has been talk of withdrawing the 4,000 strong forces from the country as early as next month.