The United States has called on Rwanda to stop supporting armed rebel groups in neighbouring Democratic Republic of Congo after a U.N. investigation implicated senior Kigali officials.
Fighting in Congo continued over the weekend in hills near the Rwandan border between forces loyal to Kinshasa and fighters from the so-called M23 mutiny.
The statement from the United States was the first time the long-standing ally of Rwandan President Paul Kagame has directly addressed the issue of the country's alleged involvement in the Congo mutiny.
Rwanda has denied the contents of an addendum to a report by U.N. experts, released last week, which provided the strongest evidence yet that officials of Kagame's government were providing military and logistical support to armed groups in Congo.
The groups include M23, a band of several hundred fighters led by Bosco Ntaganda, a mutinous army general with past links to Rwanda who is sought for arrest by Congo and also wanted by the International Criminal Court for war crimes.
"We are deeply concerned by the report's findings ... and have asked Rwanda to halt and prevent the provision of such support from its territory," Victoria Nuland, spokeswoman for the U.S. State Department, said in an emailed statement on Saturday.
Rights groups including Amnesty International and Global Witness have called on the United Nations and aid donors to Rwanda to take action in the wake of the report.
"The UK and U.S. governments are the largest bilateral donors to Rwanda ... They cannot stand by and watch a regime they bankroll orchestrating a new war in Congo," Global Witness said in a statement on Friday.
Rwanda's Foreign Minister Louise Mushikiwabo said last week that she regretted the publication of the "one-sided" U.N. report and vowed to disprove the allegations levelled against Rwandan officials, including defence minister James Kabarebe and several top military figures.
Rwanda is bidding for a seat on the U.N. Security Council next year.
On Friday, Congo's president Joseph Kabila blamed the unrest on "dark forces, national and foreign" during a speech on national television, but did not mention Rwanda by name.
Kabila called off Saturday's annual independence day celebrations as a mark of respect for the victims of the fighting, which has seen more than 200,000 people flee their homes since April, and has pushed the total number of Congo's displaced above 2 million for the first time since 2009.
M23 fighters and government troops clashed on Saturday and Sunday according to local witnesses, who said the mutineers had attempted to seize a key road but were pushed back.
M23 spokesman Vianney Kazarama said his forces had come under attack from government troops near the town of Ntamugenga, in the eastern province of North Kivu, where thousands of people are living rough after fleeing the fighting.
Kazarama said his fighters had pulled back for humanitarian reasons, allowing the Congolese army to take back territory.