DR Congo soldiers sought to stave off a rebel advance on the key eastern city of Goma on Monday as neighbouring Rwanda — accused of backing the rebels — charged that Kinshasa forces had bombed its territory just across the border in the powderkeg region.

The DR Congo army “has deliberately this evening bombed Rwanda using T55 tanks and mortar bombs,” General Joseph Nzabamwita told AFP, saying the assault had targeted the area around the airport in Gisenyi, located just a kilometre (half a mile) from the border.

Nzabamwita said the Democratic Republic of Congo army had also fired anti-aircraft missiles at nearby Mount Rubavu and that in all two civilians had been killed and seven others injured and taken to hospital in Gisenyi.

He said casualty numbers would likely rise further as others were brought in from local health centres.

A DR Congo army spokesman said no cross-border attack had been ordered and that it may have been the work of a lone individual.

“An investigation is under way,” Colonel Olivier Hamuli told AFP. “If that was done there was no formal order from the military hierarchy. If it’s an isolated act it involves only one individual.”

On the other hand, he claimed that mortar fire had been aimed at DR Congo from Rwanda in recent days and that soldiers had been wounded.

Amid a looming humanitarian crisis, fresh fighting broke out Monday on the outskirts of Goma, where only a kilometre now lies between government forces and the rebels massed at the city’s gates.

Witnesses reported weapons fire in districts to the north and northwest of Goma, the main city in the mineral-rich region, causing residents to flee south or towards the Rwanda border.

Earlier Monday, the rebels fired mortars in the direction of the airport on the eastern edge of the city as well as an army base, a Western military source said.

One of the mortars struck a hotel, and a worker at the Heal Africa hospital said six people were admitted there with injuries from the shelling.

Kinshasa had dismissed a rebel demand for direct talks as “irrational rantings” and said the M23 rebels were “fictitious forces put in place by Rwanda to hide its criminal activities in DR Congo.”

“We prefer to negotiate with Rwanda, the real aggressor,” spokesman Lambert Mende told AFP.

The United Nations has also charged that the rebels are backed by Rwanda as well as Uganda, charges both countries deny.

UN peacekeeping chief Herve Ladsous said the United Nations could not confirm Rwandan backing but said M23’s “attacking forces are well-equipped and very well-supplied”.

— Rebels to fight government ‘until it falls’ —

The mineral-rich region has long been a powderkeg, the launchpad of rebellions dating back to 1996, with Rwanda and Uganda both playing active or behind-the-scenes roles in much of the warfare.

The rebels say they plan to fight the government in Goma “until it falls”, and the United Nations warned they have a real possibility of capturing the city.

In New York, France’s UN ambassador said Paris would introduce a UN Security Council resolution on Monday seeking greater international sanctions against the M23.

The resolution could come to a vote as soon as Wednesday.

The UN Security Council, after an emergency meeting on Saturday, demanded an end to the M23 advance and a halt to “any and all outside support”.

M23 leader Sultani Makenga was hit with US and UN sanctions last week, accused of atrocities including masterminding killings, rapes, abductions and recruiting child soldiers.

The EU and Britain have also expressed alarm at the violence, which has displaced thousands of civilians and flared up again after a three-month truce last week.

The African Union on Monday demanded the rebels “immediately and unconditionally” put an end to their offensive.

Goma residents who had crossed into Rwanda said the M23 was fighting the Republican Guard while national army troops were busy looting.

UN chief Ban Ki-moon vowed Sunday that some 1,500 “quick reaction” peacekeepers would stay in Goma. They are among about 6,700 troops in Goma’s Nord Kivu province, backing government forces against the rebels.

In New York, UN peacekeeping spokesman Kieran Dwyer said UN attack helicopters have staged cannon and rocket strikes against the rebels but have not been able to stop the steady advance towards Goma.

The M23 rebels are former soldiers who mutinied in April after the failure of a 2009 peace deal that integrated them into the regular army.

The fighting is the most serious since July, when UN helicopters last went into action against the M23.

The former Belgian colony, known as Zaire under the dictator Mobutu Sese Seko who was toppled in 1997, remains one of the world’s least developed countries despite a wealth of cobalt, copper, diamonds and gold.

Since 1998 more than three million people are estimated to have died from combat, disease and hunger and 1.6 million been left homeless.

In peaceful times, Goma is the starting point for tourists wishing to see endangered mountain gorillas in nearby Virunga National Park.