(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.
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.