A group of 64 organizations mainly from the Democratic Republic of Congo sent a letter asking the European Union to cancel a critical minerals partnership with Rwanda because of its support for a rebel group in eastern Congo.

Rwanda-backed M23 rebels took the Congolese trading hub of Goma last week, leaving thousands dead and wounded and raising concerns of a regional war. Congo and United Nations experts say M23 has been smuggling Congolese minerals to Rwanda to help pay for their rebellion.

“The EU must urgently reassess any mining project involving Rwanda, or risk legitimizing the illegal exploitation of DRC resources and indirectly financing war crimes, human rights violations, and regional instability,” according to the letter which was signed by 64 NGOs and sent to EU commissioners and members of parliament Tuesday.

The EU signed a memorandum of understanding last February to support governance, transparency, and infrastructure for mineral processing and refining in Rwanda. The EU and its member states also plan to invest more than €900-million ($934-million) in the country under their Global Gateway program, including funding for critical mineral, health and climate initiatives.

Rwanda exports minerals including tungsten, tin and gold. The International Monetary Fund estimates it exported $1.3-billion worth of gold last year and could ship nearly $1.9-billion in 2025. The nation is also the world’s second-largest source of tantalum, used in most portable electronics.

Rwandan President Paul Kagame told CNN in an interview broadcast Monday that he didn’t know about mineral smuggling from Congo to Rwanda.

“People who are benefitting from minerals of Congo more than anybody else are South Africa and these other Europeans who are making noise about it,” Kagame said.

Kagame also denies supporting the rebels or sending troops to eastern Congo, which has suffered three decades of conflict since the aftermath of the 1994 Rwandan genocide.

M23 says it’s protecting the rights of Tutsis and the speakers of the Rwandan language in Congo. Kagame blames the conflict on Congo’s inability to govern its mineral-rich eastern provinces, where more than 100 armed groups are active.

M23 currently controls mines in eastern Congo that are among the largest sources of tantalum in the world. The group makes more than $800 000 a month taxing the trade from the mines, according to a report by UN experts released last month.