Rwandan-backed M23 rebels in eastern Democratic Republic of Congo (DRC) battled militiamen allied with the government on Tuesday as regional countries tried to give fresh impetus to faltering peace initiatives.

M23's swift advance since January has seized eastern Congo's two largest cities, resulted in thousands of deaths and forced hundreds of thousands more from their homes.

Southern and East Africa countries have made repeated diplomatic pushes to resolve the conflict amid fears it could spiral into a larger regional war.

The latest setback to those efforts came on Monday when the M23 rebels went back on a pledge to withdraw from the strategic town of Walikale and accused the Congolese army of failing to halt its own offensive operations there.

The rebels and pro-government milita fighters known as Wazalendo battled on Tuesday in North Kivu and South Kivu provinces, residents said.

In North Kivu, a second day of clashes raged near the banks of Lake Edward, which straddles the border between Congo and Uganda, said Muhindo Tafuteni, a local civil society activist.

In South Kivu, fighting took place in several towns north of the provincial capital Bukavu, which M23 captured in February, residents said.

REGIONAL DIPLOMACY

Leaders from the main Southern and Eastern Africa political blocs had met on Monday to advance a plan aimed at securing a ceasefire in a conflict rooted in the long fallout from the 1994 genocide in Rwanda and competition for control of mineral riches.

In a statement afterwards, they said they had appointed five former heads of state to facilitate the peace process.

The appointees are Nigeria's Olusegun Obasanjo, South Africa's Kgalema Motlanthe, Ethiopia's Sahle-Work Zewde, Kenya's Uhuru Kenyatta and Central African Republic's Catherine Samba Panza.

Congo's presidency said the new panel would name a mediator to replace Angolan President Joao Lourenco, who withdrew from the role on Monday following years of efforts to ease tensions between Rwanda and Congo.

Rwanda's government, which has been sanctioned by several Western countries for supporting M23 with arms and troops, said the summit was "fruitful".

Rwanda denies supporting M23 but also says its forces are acting in self-defence against Congo's army and militias hostile to Kigali.

M23 says the conflict can only be resolved through negotiations between the rebels and Kinshasa.

A meeting was scheduled last week in Angola after Tshisekedi dropped his longstanding refusal to negotiate with M23, but the rebels withdrew in protest at new European Union sanctions. 

Even as regional countries met to talk peace, there were reminders of the risk of escalation.

In an interview with the BBC, President Evariste Ndayishimiye of Burundi, whose troops have fought in support of Congo's army against M23, said that Rwanda had a plan to attack Burundi.

"Burundians will not accept to be killed as Congolese are being killed," he was quoted as saying in a report published on Tuesday, adding he wanted to resolve the problem through dialogue.

Burundi and Rwanda have long had tense relations, but officials from the two sides have met in recent weeks.

"These comments are surprising because Rwandan and Burundian defence and security institutions have actually been meeting to discuss how to secure our common borders," Rwanda's government spokesperson Yolande Makolo said.