KINSHASA (Reuters) - Democratic Republic of Congo is pushing Apple Inc ( AAPL ) for information about its supply chain over concerns it may be tainted with conflict minerals sourced from the country, international lawyers engaged by Congo said on Thursday.

Congo, particularly its eastern region, has been plagued by violence since the 1990s, killing millions as struggles over national identity, ethnicity, and resources saw neighbouring countries invade and a myriad of armed groups spring up.

Conflict has arisen over the control of illicit trade in tin and gold as well as in coltan and tantalum - widely used in cell phones and computers - all mined in Congo before being smuggled out through neighbouring Rwanda, Uganda and Burundi.

In September 2023, Congo President Felix Tshisekedi met with international law firm Amsterdam & Partners LLP to investigate the supply chain of tin, tungsten and tantalum - known as 3T minerals - due to concerns about illegal exports, the law firm said.

It said it had notified Apple ( AAPL ) CEO Tim Cook on Monday of a series of questions based on fears about its supply chain and also wrote to Apple ( AAPL ) subsidiaries in France, demanding answers within three weeks.

"Although Apple ( AAPL ) has affirmed that it verifies the origins of minerals it uses to manufacture its products, those claims do not appear to be based on concrete, verifiable evidence," Amsterdam said in a statement on Thursday.

"The world's eyes are wide shut: Rwanda's production of key 3T minerals is near zero, and yet big tech companies say their minerals are sourced in Rwanda," it said.

Apple ( AAPL ) did not immediately reply to an emailed request for comment. The company, which does not directly purchase, procure or source primary minerals, has been openly auditing its suppliers for several years and publishing its findings.

In a report last year, it said that 100% of identified smelters and refiners in the supply chain for all applicable Apple ( AAPL ) products manufactured in 2023 had participated in an independent third-party conflict minerals audit for 3T minerals and gold (3TG).

"We found no reasonable basis for concluding that any of the smelters or refiners of 3TG determined to be in our supply chain as of December 31, 2023 directly or indirectly financed or benefited armed groups in the DRC or an adjoining country," the Apple ( AAPL ) report said.

The Amsterdam statement coincided with the release of a report by the law firm accusing Rwanda and private entities of laundering 3T and other conflict minerals from Congo.

Rwanda and Congo's governments did not immediately respond to requests for comment.

Congo is the world's leading producer of tantalum, followed by Rwanda. It is also the number one producer of copper and cobalt, a key ingredient in electric batteries.

Most of Congo's mineral resources are concentrated in the east, where insecurity has worsened since a rebel group known as the M23 made a major comeback in March 2022.