The Rwandan government has consistently denied allegations by Congolese officials and United Nations investigators that it is fomenting and supporting the Tutsi-dominated M23 rebel movement in Congo's mineral-rich North Kivu province, long a tinderbox of regional ethnic and political tensions.
"It's not a rebellion, it's an invasion. We didn't think that the Rwandan army would be throwing all its might into Congolese territory," Erneste Kyaviro, spokesman for North Kivu governor Julien Paluku, told Reuters by telephone.
Kyaviro appealed for a forceful response by the international community, especially Western nations, to pressure Rwanda to halt its alleged support for the rebellion.
"You don't need a single shot fired to stop Rwanda," he said, saying countries like the United States, Britain, Norway and Belgium should halt their aid to landlocked Kigali to put an end to M23 operations in Congolese territory.
"We need the help of the whole world," he said, adding Rwanda had deployed elite troops along the border near Goma.
No immediate reaction was available from Rwanda's presidency or foreign ministry, which have in the past strenuously rejected the accusations of Rwandan support for the Congolese insurgency.
The rebels, described by U.N. officials as apparently well-equipped and growing in number, drove back the Congolese government army in a determined offensive over the last few days, forcing U.N. peacekeepers to withdraw into isolated operating bases in the hilly countryside. One Indian U.N. soldier was killed in a rebel attack last week.
The rapid M23 rebel advance has opened the way for a possible assault on the North Kivu provincial capital Goma, where U.N. peacekeepers have reinforced their positions.
Residents reported that U.N. armoured vehicles were guarding major crossroads of the city and also patrolling the outskirts.
The latest fighting in North Kivu has once again displaced thousands of civilians and raised tension between uneasy neighbours Congo and Rwanda in the Great Lakes region at the heart of Africa. The rebel successes have also embarrassed the army and government of Congo President Joseph Kabila.
M23 political commissar Colonel Vianney Kazarama also denied the rebels received any support from Rwanda. "We have the support of the population ... We took many weapons in Bunagana, Rutshuru, and Rumangabo. Are these places in Rwanda?" he said.
In a report last month, U.N. experts laid out evidence of high-ranking Rwandan military officials backing the Congolese rebels and the United States, a key ally of Rwandan President Paul Kagame, has also called on Kigali to halt this support.
The so-called M23 insurgents, who include mutineers from the Congo army, take their name from a March 2009 peace deal that ended a previous Tutsi-led rebellion in North Kivu.
Since March, hundreds of ex-rebels have defected from the army in support of a renegade general, Bosco Ntaganda, wanted by the International Criminal Court for suspected war crimes.
Like the 2004-2009 rebellion, the current mutiny has its roots in ethnic and political wounds dating back to Rwanda's 1994 genocide. Later invasions of Congo by Rwandan forces and Kigali's backing of Congolese rebels fuelled two successive wars that killed several million people.
CONGO TO U.N. PEACEKEEPERS: "GET ENGAGED"
Kyaviro said the Congolese army, which has melted away before the M23's advance, was reinforcing its units at Goma. But he appealed to the U.N. peacekeeping mission in Congo, MONUSCO, to be more robust in its response to the rebels' offensive.
"They (the peacekeepers) are not here to do tourism, they should get engaged," he said, adding that U.N. troops had simply shut themselves into their bases when the rebels took Bunagana, Rutshuru and other locations north of Goma in the past days.
Rebel commanders and MONUSCO say the insurgents have since pulled back from some of the seized positions. A witness told Reuters on Tuesday that M23 fighters continued to occupy a military base in Rumangabo, just 40 km (25 miles) north of Goma.
"The M23 forces appear to be well equipped and supplied, their numbers have increased in recent weeks," a U.N. official, who asked not to be named, said late on Monday, adding the rebels might move west towards the Masisi area of North Kivu.
"That would again be of great concern because it is a stronghold area and there's the possibility then of actually threatening Goma on two fronts," the U.N. official said.
The official said MONUSCO was helping the Congolese army reinforce the road from Rutshuru to Goma to prevent further advances by M23 and ensure government soldiers were able to return to their positions to help protect civilians.
Thousands of people have been displaced, but the exact death toll from the recent fighting is not known. The U.N. Security Council has condemned the rebel attacks.
In The Hague, the International Criminal Court jailed Congolese warlord Thomas Lubanga Dyilo for 14 years for recruiting child soldiers in eastern Congo.