Uganda's military on Monday denied that armed Congolese rebels sheltering in the country had crossed back into the Democratic Republic of Congo, saying they were still in their camp.

The DRC government said Sunday that at least 200 former members of M23, a mostly ethnic Tutsi rebel group defeated by the Congolese army three years ago, arrived from Uganda and took over a village in North Kivu province.

Government spokesman Lambert Mende told AFP the Congolese army was fighting two battalions installed in Ishasha village "who were supposed to be in Uganda under the responsibility of that country's authorities".

Ugandan defence spokesman Major Henry Obbo said in a statement that the rebels were still at the Bihanga army camp some 320 kilometres (190 miles) west of the capital "where they have been since 2013."

Congo's resource-rich eastern provinces have suffered years of brutal conflict, with neighbouring states backing rebel groups in a civil war against Kinshasa's authority, and roaming armed militia triggering the mass flight of terrorised civilians.

In 2012 former members of a Tutsi militia who had integrated in the Congolese army mutinied, claiming that a peace deal signed on March 23, 2009 had not been respected.

The M23 rebels wreaked havoc in the east, even managing to briefly seize the regional capital Goma.

After its November 2013 defeat at the hands of Congolese and UN forces, M23 agreed to a plan to disarm, demobilise and reintegrate its soldiers into DRC civilian life.

But the return of the former rebels has stalled, with fewer than 200 of the 1,900 sheltering in Uganda and only 13 out of hundreds left in Rwanda coming back.

During the civil war Congolese authorities denounced Rwanda and Uganda for allowing the rebel groups to use their territory as staging grounds for attacks.

More recently, they have blamed the states for "bad faith" for allowing "criminals to circulate freely" instead of extraditing them to stand trial in DR Congo.

"We sympathise with DRC on issues of belligerents but they should not use M23 rebels in Uganda (when they) should be concentrating on their country", Uganda's Foreign Minister Henry Okello Oryem told AFP Sunday.

"Let them concentrate on issues of governance in their country," he added.