Washington DC - The US on Sunday condemned "in the strongest terms" attacks by Rwandan and M23 fighters in the eastern Democratic Republic of Congo, calling urgently for a ceasefire.

In the first official remarks on the crisis under the new US administration of Donald Trump, interim UN ambassador Dorothy Shea said the US "will consider all the tools at its disposal in order to hold accountable those responsible for sustaining armed conflict, instability and insecurity in the DRC."

"We condemn in the strongest terms Rwanda's and M-23 hostilities on Goma and attacks on Sake" in eastern DRC, career diplomat Shea told an emergency session of the UN Security Council, as renewed fighting intensifies in the region after failed truce negotiations.

"Rwanda's use of advanced weaponry and systems," including GPS jamming, had endangered both UN peacekeepers and those fleeing violence, she said, calling for the actions to "stop immediately."

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She denounced the "indiscriminate" use of artillery near refugee sites.

"Congolese and Rwanda leadership, as well as leaders of the M23 and other armed groups, must issue clear orders not to target civilians," she said.

"All actors must also respect the sovereignty and territorial integrity of the DRC and put an end to all forms of support to armed groups, whether Congolese or foreign," she added.