French prosecutors have closed a case filed by Democratic Republic of Congo accusing Apple subsidiaries of using conflict minerals in its supply chain, according to a document seen by Reuters on Thursday.

Congo filed criminal complaints against Apple subsidiaries in France and Belgium, its lawyers said in December. Apple said then it strongly disputed the allegations and had told its suppliers they must not use the minerals in question sourced from Congo or Rwanda.

In the document seen by Reuters and dated February 18, the Paris prosecutor's office said allegations of money laundering and deceptive business practices were "not sufficiently well-founded" and closed the case - meaning it will not proceed with the complaint.

The office invited Congo to contact a different office "with jurisdiction over war crimes".

The prosecutor's office and Apple did not immediately respond to an emailed request for comment on Thursday.

William Bourdon and Vincent Brengarth, lawyers working for Congo in France, described the decision as a "very partial dismissal" that they intended to challenge, citing the "extreme seriousness of the facts denounced and the need to identify and prosecute those responsible."

Congo is a major source of tin, tantalum and tungsten, so-called 3T minerals used in computers and mobile phones. Some artisanal mines are run by armed groups involved in massacres of civilians, mass rapes, looting and other crimes, according to U.N. experts and human rights groups.

Since the 1990s, Congo's mining heartlands in the east have been devastated by waves of fighting between armed groups, some backed by neighbouring Rwanda, and the Congolese military.

The complaints filed in France and Belgium were prepared on behalf of Congo's justice minister. Belgium appointed an investigating magistrate in response, a lawyer for Congo said in January.