( CNN ) -- French forces have seized a significant arms cache in northern Mali believed to have belonged to Islamist jihadist groups , including `` tons '' of heavy weapons , suicide belts and equipment for improvised explosive devices , France 's defense minister said Friday . Speaking from Bamako , Mali , on Europe 1 radio , Jean-Yves Le Drian said he 'd toured the `` sanctuary of al Qaeda in Mali '' and saw the radical Islamists ' arsenal sitting in caves . `` ( The arms were ) destined to break the security of our own territory , '' the minister said . French and allied forces , including Malian and Chadian troops , have made significant inroads in recent weeks combating Islamist extremist fighters . Still , fighting continues in mountainous areas in the northeastern part of the West African nation , and Le Drian said that security in the key northern city of Gao remains a concern as well . France will begin to reduce its troop levels in Mali next month in an effort to have West African forces , with the support of the United Nations , take over and maintain security in the country , French Foreign Minister Laurent Fabius said earlier this week . When asked Friday if France 's intervention in Mali is mostly complete , Le Drian said that his country has `` accomplished a big part of the mission , but the last part is the hardest . '' Beyond combing through their weapons , French forces are using DNA tests to identify some of the slain Islamist fighters , Fabius said . Those tests could establish whether Moktar Belmoktar or Abdelhamid Abou Zeid -- two men who have been major figures in al Qaeda in the Islamic Maghreb -- are among the dead , as has been suggested by others but not confirmed by France . French citizens among radical fighters in Mali , minister says . Islamist extremists carved out a large haven in northern Mali last year , taking advantage of a chaotic situation after a military coup by the separatist party MNLA . The militants banned music , smoking , drinking and watching sports on television . They also destroyed historic tombs and shrines . French involvement in the conflict began on January 11 , the day after militants said they had seized the city of Konna , east of Diabaly in central Mali , and were poised to advance south toward Bamako , the capital . Nearly 4,000 French soldiers are now deployed in Mali , according to the French Defense Ministry website , alongside about 6,300 troops from Chad and the African-led International Support Mission to Mali .
France 's defense minister reported seeing sizable arms caches in northern Syria . The Islamist fighters ' weapons were ` ` destined to break ( France 's ) security , '' he says . France accomplished much of its mission , but ` ` hardest '' part remains , he says .