Congo's lush and forested eastern borderlands have long served as an operating base for multiple armed groups. As the conflict there intensifies, the mineral-rich eastern provinces have also become a bloody playground for a rising number of countries, including Rwanda, Burundi and Uganda, as well as regional forces from three southern African nations.

At the same time, the Democratic Republic of Congo and Rwanda are involved in a bitter spat. Each blames the other for supporting various armed groups in Congo's eastern provinces of North and South Kivu, Ituri, and Tanganyika.

The flaring violence, with its volatile mix of rebels, militias, state and regional forces, private military contractors and local vigilantes, each driven by diverse interests and grievances, is fueling fears the fighting could spill over Congo's border.

Here is a rundown of the main players:

M23 and other armed groups

More than 250 local and 14 foreign-armed groups are active in eastern DRC, according to a 2023 survey undertaken by the government's disarmament and reintegration program, P-DDRCS.

March 23 Movement, or M23, is the most prominent of these. The group, which is primarily made up of ethnic Tutsis, says it is fighting to defend Congolese Tutsis from discrimination and extremist groups such as the Democratic Forces for the Liberation of Rwanda (FDLR), an ethnic Hutu rebel militia. Rwanda's President Paul Kagame has long viewed the FDLR as an existential threat to his nation.

After laying dormant for several years, M23 began to reemerge in late 2021. Since then, it has only grown more formidable. M23 conducts itself "increasingly as a conventional army, rather than an armed group" and boasts "increasingly sophisticated firepower and equipment," according to UN experts.

More recently, clashes between M23 and Congo's armed forces have intensified, with the rebels steadily advancing towards Goma, North Kivu's lakeside capital, in the last few days.

"The whole family was so frightened that we decided to leave the city," Goma resident Jean de Dieu Kulondwa told DW.

His family adds to the more than 5.5 million people displaced in DRC's east in what is one of the world's biggest humanitarian catastrophes.

Rwanda's involvement with M23

The United Nations, Human Rights Watch and other independent observers have documented Rwandan support to M23 rebels, "including transfers of arms and ammunition, facilitating recruitment, and even direct combat support by the Rwanda Defence Force," notes a 2023 analysis for the International Peace Institute's Global Observatory.

Most recently, the Rwandan army has been accused of using sophisticated weapons such as surface-to-air missiles (SAM) inside Congo. An unpublished document by the UN's MONUSCO peacekeeping mission in eastern Congo, cited by AFP news agency earlier in February, noted that using a mobile SAM system within the country "indicates an escalation of conventional force conflict."

In turn, the Tutsi-led Rwandan government of President Kagame accuses Congo of backing the FLDR, its sworn enemy. The insurgent group was founded by Hutu fighters and families who fled to Congo after the 1994 Rwandan genocide, which saw nearly 1 million Tutsis slaughtered by Hutu extremists.

Burundi's covert operation in Congo

Some 1,000 Burundian troops are reportedly in North and South Kivu as part of a covert operation. Reuters, citing an internal UN report seen by the news agency, said the Burundian soldiers arrived in the DRC in October 2023 and are fighting in Congolese army uniforms.

This is separate from the deployment of Burundian forces to eastern DRC as part of the East African Community regional force, which withdrew in December 2023 after Congolese President Felix Tshisekedi refused to renew its mandate.

Burundi's troops are reportedly mostly fighting Congo-based armed rebel groups opposed to the Burundian government, such as the RED-Tabara militia, which is responsible for attacks on Burundi and which Burundi accuses Rwanda of funding and training.

Under a bilateral agreement signed in 2021, Congo's government is picking up the bill for the deployment, which is said to cost $5,000 (€4,634) a month for each Burundian soldier.

"By supporting the DRC, Burundi is supporting itself, as it is helping to neutralize the RED-Tabara rebels," Congolese political scientist Christian Moleka told DW. At the same time, Burundi is helping "cut off the influence that Rwanda, via pro-Tutsi militias, can exert on the RED-Tabara movement."

Uganda in joint operation against ADF militia

Ugandan troops have been fighting in eastern DRC since 2021 as part of a joint operation to dismantle the Allied Democratic Forces (ADF), a militant group affiliated with ISIS. The ADF, designated a terror group by the United States and Uganda, originated in Uganda in the 1990s but now operates from North Kivu and carries out attacks both in Uganda and in Congo.

"Although this group has received less attention than the M23, it is at least as deadly," Congo expert Kristof Titeca from Belgium's University of Antwerp told DW, adding that joint operation between Congolese and Ugandan forces has been "particularly effective" in the past six months.

African regional forces and European mercenaries

When DR Congo's Tshisekedi kicked out the East Africa regional force in December 2023, he immediately welcomed troops from South Africa, Malawi and Tanzania under a Southern African Development Community (SADC) mission. In mid-February, South Africa's government said that another 2,900 of its soldiers were being mobilized for the SADC operation, which has a mandate until December 2024.

Two private military contractors also have around 1,000 private soldiers in Goma. The first, Bulgarian-registered Agemira, is run by a French national and includes retired French military personnel. Agemira is contracted to provide aircraft maintenance for the Congolese army.

The second, Congo Protection, is managed by a Romanian ex-member of the French Foreign Legion and employs mostly Eastern European former soldiers. While Congo Protection is contracted to train Congolese army units, its soldiers have also manned defense posts alongside its Congolese army trainees when it has come under rebel attack, according to UN experts.

Local militias added to the mix

In 2022, Tshisekedi called for young men and women in the east of Congo to form vigilance groups to fight against M23. Late last year, a government decree legalized the militias within its army. It brought local self-defense and allied armed groups together in an alliance known as Wazalendo  — a Swahili word that means patriots  — and gave them military and financial support. Even elements of the feared FLDR militia group have reportedly joined.

Uganda-based security analyst David Egesa said that arming groups to fight M23 might help in the short term but warned it could also strengthen militia groups.

"DR Congo might discreetly allow the militia to work together against M23. But such a twisted game could, in the longer term, embolden the militias," Egesa told Anadolu Agency, a Turkish news agency. "It's a dangerous situation."

Zanem Nety Zaidi in Goma and Sandrine Blanchard contributed reporting to this article.

Edited by: Chrispin Mwakideu