“It’s a step in the right direction,” government spokesman Lambert Mende told reporters of the withdrawal. President Joseph Kabila would soon start “listening to the grievances” of the mainly Tutsi rebels as part of peace negotiations, he added.

Security remains fluid following the M23’s 12-day occupation of Goma, despite over 160 police reinforcements arriving by boat at the lake port to beef up some 300 colleagues who arrived on Saturday.

Alongside United Nations peacekeepers, a few police patrols were seen on the streets of Goma, a city of around one million people that is the hub of the resource-rich area. Some 600 government soldiers are also reported to be on their way to Goma.

But Rwanda also said on Sunday that Hutu extremist FDLR rebels based in DR Congo – Rwandans who fled the country following the 1994 genocide of mainly Tutsis – had clashed on the border with Rwandan troops, but were repulsed.

UN experts have accused Rwanda and Uganda – which played active roles in DR Congo’s 1996-2003 wars – of supporting M23, a charge both countries deny.

But Rwandan army spokesman Joseph Nzabamwita accused the FDLR rebels of “having received heavy arms and ammunition” from DR Congo’s army “to destabilise Rwanda.”

The UN-backed Radio Okapi – a key source of independent news, broadcasting in French and four local languages – has also been jammed since late Saturday, officials said, after it aired an interview with M23 political leader Jean-Marie Runiga.

Its jamming is “troubling and regrettable”, head of UN mission in DR Congo Roger Meece said in a statement.

The rebels’ lightning capture of Goma last week – eight months after they launched their uprising – sparked fear of a wider war and major humanitarian crisis. Their pullout was widely welcomed.

The region has already been the cradle of back-to-back wars that embroiled other nations from 1996 to 2003 fought largely over its vast wealth of copper, diamonds, gold and key mobile phone component coltan.

Residents were wary of the arrival of government soldiers, who, like the rebels, have been accused of the killings of civilians, rape and looting during the latest unrest.

“They used to intimidate you and ask you for money,” said Angeline, a Goma resident who only gave her first name.

“Of course we’re a little worried... what we want is peace,” she added, sitting at her small market stall, empty of goods.

Singing songs and waving guns, M23 fighters crammed on to a convoy of looted trucks left Goma on Saturday, taking heavy weaponry and ammunition seized when Congo’s army fled in disarray.

But the rebels remain just outside Goma, having pledged to withdraw only 20 kilometres under a regionally brokered deal, with complex negotiations now to focus on their demands, which include political reform.

Jason Stearns, an independent analyst, warned the withdrawal “is just a tactical retreat and the war is far from over”.

UN peacekeepers, who were unable to stop the rebel sweep across the east, said they had no plans to boost its current force of 1,600 troops in Goma, said spokesman Madnodje Mounoubai.

Under the deal agreed by the rebels, the M23 will post 100 men at Goma airport alongside similar numbers of government troops, soldiers from neighbouring Tanzania and UN peacekeepers.

M23 was founded by former fighters in a Tutsi rebel group whose members were integrated into the regular army under a 2009 peace deal that they claim was never fully implemented. Several of its leaders have been hit by UN sanctions over alleged atrocities.

Decades of conflict between multiple militia forces – as well as meddling by regional armies – have ravaged Congo’s east.

Britain on Friday froze US$33.7 million in aid to Rwanda following what it said was “credible and compelling reports of Rwandan involvement with M23”.

Aid agencies are struggling to cope with the newly displaced, with some 285,000 people having fled their homes since the rebels began their uprising in April.