Rwanda and Uganda have been surreptitiously supporting a violent rebellion in neighboring Democratic Republic of Congo, or DRC, according to a confidential report from the United Nations Security Council.

The report was composed by U.N. experts who were monitoring international compliance with sanctions against Congo, according to Reuters. It revealed that the rebel group there, M23, was acting under the auspices of none other than Rwanda’s own Defense Minister General James Kabarebe. It also found that Uganda had supplied M23 with “troop reinforcements ... weapons deliveries, technical assistance, joint planning, political advice and facilitation of external relations.”

Both Ugandan and Rwandan officials have dismissed the findings.

The allegations against Uganda and Rwanda are very serious. According to a report from global watchdog organization Human Rights Watch last month, M23 is committing war crimes against civilians in the DRC. The atrocities include child soldier recruitment, frequent rapes and summary executions.

M23 was formed in the spring of this year, but the roots of their dissent run deep. This has much to do with old conflicts in neighboring countries like Rwanda and Uganda.

M23 fighters say they are protesting an unjust and ineffectual government. And although their tactics are reprehensible, those complaints are not without merit. Despite an abundance of natural resources, the country is afflicted by hunger and poverty. Infrastructure is essentially non-existent. The government is headed by Joseph Kabila, whose elections to office are widely condemned as rigged, but whose citizens are too poor to stage effective protests.

The animosity between the DRC government and the administrations of Rwanda and Uganda is linked to the 1990-1994 Rwandan Civil War that pitted the Hutu and Tutsi ethnic groups against each other, a conflict that included massacres, massive displacement and genocide largely condoned by the Hutu regime.

After that conflict ended with a Tutsi victory, more than 2 million Hutus spilled into the DRC, where Tutsis also lived. Ongoing rivalries eventually kicked off the Second Congo War in 1998. This devastating clash and its ongoing aftermath have killed over 5 million people, making it the planet’s deadliest conflict since World War II.

In a conscious effort to allay tensions, central African politicians today take pains to avoid framing these conflicts in ethnic terms. But the Rwandan administration resents the government of DRC for harboring Hutu refugees, and if the U.N. report allegations are true, the M23 has become a proxy for Rwanda, and its ally Uganda, to attempt to overthrow the DRC’s leadership.

The DRC administration has long suspected Rwanda of supporting M23.

“We've taken note of this report which confirms what we already know about Rwanda and contains new information about Uganda,” said government spokesman Lambert Mende to Reuters. “We're in contact with our neighbors in Uganda over these very serious allegations.”

The DRC has also demanded that sanctions be placed on targeted officials in the Rwandan and Ugandan administrations.