The United States has accused Rwanda of involvement in a deadly attack on a camp for displaced people in the eastern Democratic Republic of Congo, a claim dismissed as "absurd" by Kigali on Saturday.

At least nine people were killed in blasts on Friday in the camp on the outskirts of the city of Goma, local sources said.

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

DR Congo government spokesman Patrick Muyaya on Friday had also accused "the Rwandan army and its M23 terrorist supporters" of being responsible in a statement on X, the former Twitter.

Rwandan government spokesperson Yolande Makolo described the US comments as "ridiculous", in a post on X.

"How do you come to this absurd conclusion? The RDF, a professional army, would never attack an IDP camp," she said.

"Look to the lawless FDLR and Wazalendo supported by the FARDC (the Congolese armed forces), for this kind of atrocity," she added.

The FDLR, or Democratic Forces for the Liberation of Rwanda, is an armed ethnic Hutu group operating in Congo's east for 30 years, while Wazalendo is fighting the M23 alongside the Congolese army.

The origin of Friday's blasts has not been clearly established. 

According to witnesses, government forces positioned near the camp had been bombarding the rebels on hills further west since early morning and, according to a civil society activist, "the M23 retaliated by throwing bombs indiscriminately".

"Horror in its most serious form! A bomb on civilians, deaths, children! A new war crime," said the government spokesman Muyaya.

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.

France's President Emmanuel Macron also this week called on Rwanda to end its backing for M23 rebels and withdraw its troops from DR Congo territory. 

President Paul Kagame in turn has demanded that the DR Congo 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 DR Congo and Rwanda and announcing a pathway to reduce tensions. 

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