The rebel militia M23 - widely believed to be backed by Rwanda - holds the city of Goma but was taken by surprise on Thursday in the village of Sake, 26 kilometres away, when government soldiers launched a counteroffensive.

At Mugunga, a sprawling refugee camp halfway between Goma and Sake, the numbers of displaced seeking shelter have soared.

''Before [the fighting] we had 15,000 people here,'' Jean Sindi Dunia, the principal police commissioner in Mugunga's third camp said. ''Now we have displaced people arriving from Kanyaruchina [another camp north of Goma]. We … think the numbers have tripled.''

Those fleeing find only overcrowded, unsanitary conditions in the poorly supplied camps.

''There is famine in the camp since last Sunday,'' Mr Dunia said. ''We received many displaced with nothing to eat. Even to find shelter for them is very difficult. We ask the international agencies to come to help these displaced people. The problem is food. People don't have enough to eat.''

The speed with which Goma fell while under the eyes of United Nations peacekeepers has raised the spectre of a more protracted conflict in the DRC.

M23 consists mainly of soldiers who mutinied from the DRC's army between March and May this year. The rebels claim the Congolese government failed to fully implement the March 23, 2009, peace agreement - hence the name M23. The agreement was supposed to have integrated a precursor of M23, the National Council for the Defence of the People, known as CNDP, into the army.

The International Crisis Group says Congolese authorities only feigned the integration of the CNDP into political institutions, and the group appears to have only pretended to integrate into the Congolese army.

The advance of M23 has uprooted about 60,000 civilians, say UN humanitarian officials. There have been reports of summary executions, the widespread recruitment and use of children, unconfirmed cases of sexual violence, and other serious human rights abuses.

About 500,000 people have been displaced since April, when the M23 rebellion began. With state control collapsing in large swaths of the east of the DRC, there are severe food shortages and a heightened risk of cholera and other diseases.

M23 is thought to be backed by neighbouring Rwanda. A UN report released this week said the Rwandan military commands and supports the rebel force, while Uganda provides more subtle, but nonetheless decisive, backing to the rebels. The report said Rwanda provides equipment and direct reinforcements to the M23 rebels, with the de facto chain of command of M23 ending with the Rwandan Defence Minister, James Kabarebe. Rwanda and Uganda have rejected the accusations, but several donors have suspended aid to Rwanda in light of the accusations.

In response to the UN report, Britain issued a statement on Thursday saying there was ''credible and compelling'' evidence of Rwandan support for the rebels.

The UN Security Council adopted a resolution in which it strongly condemned the latest wave of attacks by M23 and demanded its immediate withdrawal from Goma.

The Congolese President, Joseph Kabila, met the Rwandan President, Paul Kagame, for talks on Tuesday, mediated by the Ugandan President, Yoweri Museveni, but no deal was announced. While the Congolese army is much larger than M23 - numbering about 150,000 - the spaces between the country's cities in are immense.

Analysts say it is in Rwanda's interest to exert influence over areas of eastern Congo, where an estimated 1 million Hutu refugees fled after perpetrating the genocide against Tutsis and moderate Hutus in 1994. This enables Rwanda to maintain a buffer zone and exploit the trade and trafficking of minerals.

Guardian News & Media