An advance by Rwanda-backed M23 rebels has marked the gravest escalation in more than a decade of a long-running conflict in eastern Congo, rooted in the spillover of Rwanda's 1994 genocide into Congo and the struggle for control of Congo's vast minerals resources.

Rwanda rejects allegations from Congo, the United Nations and Western powers that it supports M23 with arms and troops.

The US said a day earlier that it was imposing sanctions on a Rwandan government minister and a senior member of an armed group for their alleged roles in the conflict.

In a diplomatic note seen by Reuters earlier this month, the US said that stability in the region will require the Rwandan military "to withdraw its forces and advanced weaponry" from Congo.

"Secretary of State Marco Rubio spoke with Kenyan President William Ruto to discuss the ongoing conflict in the eastern DRC, including the unacceptable capture of Goma and Bukavu by the Rwanda-backed M23 armed group," the State Department said.

"Both leaders reaffirmed their commitment to push for a diplomatic resolution to the crisis."

--Reuters--