The United States has blamed Rwanda in a deadly attack on a camp for displaced people in the eastern Democratic Republic of Congo, voicing alarm on the expansion of Kigali's forces and its M23 rebel allies.

"The United States strongly condemns the attack (Friday) from Rwanda Defense Forces and M23 positions on the Mugunga camp for internally displaced persons in eastern Democratic Republic of the Congo," State Department spokesman Matthew Miller said in a statement.

Miller said that the United States was "gravely concerned" by the expansion in the DRC of Rwandan forces and the M23, a mostly Tutsi group that resumed its armed campaign in the vast, long turbulent DRC in 2021.

"It is essential that all states respect each other's sovereignty and territorial integrity and hold accountable all actors for human rights abuses in the conflict in eastern DRC," he said.

The United States has repeatedly backed Kinshasa's claims that Rwanda has backed the M23, but Miller's statement amounts to an unusually direct implication.

President Paul Kagame in turn has demanded that the DRC act against Hutu forces over ties with the perpetrators of Rwanda's 1994 genocide, which mostly targeted Tutsis.

The United States has repeatedly sought to mediate between the two sides, with intelligence chief Avril Haines in November visiting the DRC and Rwanda and announcing a pathway to reduce tensions.

Secretary of State Antony Blinken earlier this year met Kagame and voiced hope that Rwanda was willing to engage in diplomacy.