The UN Security Council brushed aside Rwandan protests to release a report Thursday saying Democratic Republic of Congo rebels are recruiting fighters inside Rwanda.
Rwanda slammed the report as "flawed" and said it had been made an unfair target of UN investigations.
The report by experts monitoring the UN sanctions regime against DR Congo gave new evidence that M23 rebels had breached a peace accord made with the DR Congo government last year.
The report said there was "credible information" that M23 leaders who face UN sanctions are "moving freely in Uganda and that M23 continued to recruit in Rwanda."
Last week, the head of the UN mission in DR Congo, Martin Kobler, said there were "credible reports" that M23 was rebuilding at Ituri in northeastern DR Congo.
M23 launched a rebellion against the DR Congo government in the east of the country in 2012 and briefly took the key city of Goma.
But the rebels were beaten by government forces, backed by beefed up UN troops, in November and signed a peace accord with the government a month later.
Kobler called on Rwanda and Uganda "to do everything possible to prevent M23 elements from sheltering or training troops on their territory" so that they could start a new campaign.
UN experts have repeatedly accused Rwanda and Uganda of backing M23 or allowing the rebels to use their territory. Both deny the accusations.
While the accusations in the new report are fairly mild, Rwanda, which is a temporary member of the 15-nation Security Council, reacted with fury to the document, saying it should be rejected.
Olivier Nduhungirehe, Rwanda's deputy UN ambassador, said after council consultations that the report was based on "flawed methodology" with "a lack of sources."
"Rwanda is now commemorating the 20th anniversary of the genocide against the Tutsis," he said in reacting to the repeated allegations against his country.
"We clearly stated that we are not in the mood for continuing this punching bag exercise against Rwanda."
The experts report also said huge amounts of gold, precious stones and minerals were being smuggled out of eastern DR Congo by rebels and government army officers. AFP