France said Tuesday that its forces were engaged in heavy fighting in northern Mali and that many Islamist rebels had been killed in recent clashes. "The fighting is fierce and is continuing as we speak," Defence Minister Jean-Yves Le Drian told RTL radio in a morning interview, adding that fighting was concentrated in the Ifoghas mountains. He said there had been "many, many jihadist deaths" but refused to provide specific numbers. Le Drian said France's military intervention in Mali had cost more than 100 million euros ($131 million) since it was launched in mid-January. The French intervention backing Malian forces drove Islamist rebels from cities in the north of the West African country they had seized last year, but clashes and guerrilla attacks have continued.