Congo's M23 rebels say they will stay in Goma, which they seized last week, and will fight the Congolese army if it tries to retake it.

M23 president Jean-Marie Runiga addressed reporters in the centre of Goma on Tuesday, almost 12 hours after the rebels defied an evacuation deadline set by neighbouring nations. The International Conference on the Great Lakes Region issued a deadline of midnight Monday night.

Congo's military spokesman, Col. Olivier Hamuli, called the rebels' defiance "a declaration of war" and said the army will resume combat, although he declined to say when.

60,000 Congolese displaced

UN humanitarian agencies are expressing increased concern for the civilians of North Kivu, the Congolese province home to the recent violence.

The rebel advance in the province has uprooted about 60,000 civilians, according to the UN.

Typically, about 108,000 people are housed in internally displaced persons camps in the province. But thousands of civilians are now fleeing the areas facing increased violence.

The fighting has made it difficult for the UN to visit the refugee camps, and about 40,000 people at Mugunga III camp went without any assistance for three to four days.

Human rights abuse allegations against the rebels and national army are growing as the fighting continues.

Runiga said that the M23 now has 1,000 tonnes of arms and ammunition, including heavy artillery, abandoned by the fleeing Congo army. Six flatbed trucks carrying crates of ammunition were seen Tuesday being driven by M23 soldiers north of Goma.

Runiga said the rebels would like to negotiate with the Congolese government, but for the armed group to leave Goma, Congo would have to agree to a new set of conditions.

Congo has already said that it is willing to negotiate with M23 on the basis of the March 23, 2009 peace accord, which paved the way for the fighters to join the Congolese military.

Runiga said Tuesday that the rebels are no longer just focused on the peace accord. In April, when the rebellion began, the group said it wanted to revisit the accord, claiming that Congo had not held up its end of the bargain, failing to provide the fighters with adequate pay and proper equipment.

"Lots happened between 2009 and 2012. It is better to tackle the root causes of the issue once and for all," he said. 

At Runiga's press conference, female ushers wore Mushanana fabric, a toga-like dress typically worn by Rwandan women. The visual detail emphasized the foreign provenance of the rebels now occupying Goma, who according to the findings of the United Nations Group of Experts are financed by Rwanda, which is providing them with arms, sophisticated communications equipment as well as several battalions of troops. 

FDLR rebel group adds to violence

Highlighting the volatility of the situation, a different rebel group based in Congo, known as the FDLR, crossed into neighbouring Rwanda and attacked Rwandan army positions, according to villagers, eyewitnesses and Rwanda's military spokesman.

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M23 rebels patrol around Goma on Monday. The rebels did not adhere to regional leaders' midnight deadline to withdraw from the city. (Jerome Delay/Associated Press)

Two of the attackers were captured and are undergoing questioning, said  Rwanda's military spokesman, Brig.-Gen. Joseph Nzabamwita, while the Rwandan forces have intensified patrols on the border with Congo.

The fighting raised the possibility that Congo was directly retaliating against Rwanda, its much-smaller but more affluent neighbour, which has twice gone to war with Congo. Rwanda is now believed to be directing the M23 rebellion. 

M23 soldiers told residents in the area on Tuesday to go to Goma for their safety.

The Congo military believes this was a diversion staged by the M23 so they could retain control of Goma.

The M23 was created nearly eight months ago by former rebels who joined and then defected from the Congo army. The group is supported by Rwanda and Uganda, according to a United Nations report released last week. The M23 has been accused of human rights abuses, including executions and forced recruitment of children.

With files from CBC News