(CNN) — An emergency summit got underway in east Africa Friday in an attempt to halt an escalation in fighting in the Democratic Republic of Congo that has displaced tens of thousands of people.

Regional leaders and U.N. Secretary General Ban Ki-moon are were meeting with seven African leaders in Nairobi, Kenya, in the latest diplomatic effort to tackle what aid agencies say is developing into a major humanitarian crisis.

The talks involving Congo President Joseph Kabila, Rwanda’s Paul Kagame and Tanzania’s Jakaya Kikwete came as renewed fighting threatened to unravel a cease-fire struck between the Congolese government and rebels forces.

The conflict in country’s east is driven by unresolved ethnic hatred stemming from the killings of a half-million Tsutis by Hutu militia in Rwanda and Congo’s civil wars in 1994.

The United Nations released a statement Thursday saying the secretary-general “is deeply concerned about the ongoing violence in the eastern Democratic Republic of the Congo.”

The secretary-general “calls for an immediate cessation of hostilities and the withdrawal of forces to positions held prior to the resumption of fighting on 28 August,” the statement said, referring to when the latest wave of fighting broke out.

Ban “urges the armed groups involved in the ongoing fighting to support the current efforts to find a political solution to the crisis in the eastern DRC and to avoid activities that result in the further displacement and suffering of the civilian population.”

On Thursday, Madnoje Mounoubai, a spokesman for the U.N. in the Democratic Republic of Congo, said Tsuti General Laurent Nkunda’s rebels had battled government forces in eastern Nyzanale, North Kiva province on Thursday.

On Wednesday, Nkunda’s forces — the National Congress for the Defense of the People — fought pro-government Mai Mai militias, in Kiwanja, also in eastern Congo, said Kevin Kennedy, a spokesman for the U.N. mission.

“We encourage all the groups to restore the cease-fire,” he said.

Nkunda said his forces had not broken the cease-fire.

“We declared for a cease-fire, it was a unilateral cease-fire. And we ask the government to stop the attacks, even their allies,” he told CNN Thursday.

“So they attacked us,” he said.

“What we are asking for is only a cease-fire, then we go for peace talks and we ask the government to accept us through talks and to have a neutral mediator. That’s what we are asking. It’s not so many things.”

The rebel leader said the Mai Mai had been dressed in civilian clothing during Wednesday’s fighting, and he vehemently denied allegations that his forces had killed civilians.

“It’s not true,” Nkunda said. “These Mai Mai, these militia were in civil dress. … We asked the civilian population to get behind the front lines. So, the population were behind the front line,” he said.

“We cannot kill a civil population,” he said.

On Tuesday, the rebels battled Mai Mai fighters near Rutshuru, near Kiwanja.

Medecins Sans Frontieres (Doctors Without Borders) said surgical teams had treated 50 people from Wednesday and Thursday’s fighting.

“Thousands of people who have fled the fighting in Kiwanja have sought shelter on the road between the two towns, in churches, and even inside Rutshuru hospital,” MSF said. It did not say if the people treated were civilians.

Anne Taylor, the head of the MSF mission in Goma, issued a statement saying, “MSF provides health care to all patients without discrimination.”

Around 250,000 people were displaced as a result of fighting in recent months, the United Nations estimates.

Tensions in the Congo have festered since its civil wars in the mid-to-late 1990s and since the 1994 Rwandan genocide.

Nkunda has repeatedly blamed the Congolese government for failing to protect the Tutsi tribe from Rwandan Hutu militia in Congo. Critics have alleged Nkunda to be a puppet of Rwanda.

The ongoing conflict and humanitarian crisis kills 45,000 people in Congo every month, according to a January 2008 report from the International Rescue Committee.

Hutu rebels have been active in the jungles of eastern Congo since Rwanda’s 1994 genocide, according to the United Nations. During the 100 days of that genocide the Hutu majority killed 800,000 Tutsis and moderate Hutus, the United Nations estimates.

• In another development, a correspondent for the German newspaper Frankfurter Allgemeine Zeitung has been freed — three days after militiamen kidnapped him in the Democratic Republic of Congo, the paper said Friday.

Belgian reporter Thomas Scheen, the newspaper’s longtime Africa correspondent, was captured by Mai Mai militiamen Tuesday after getting stuck between the lines of fighting in the conflict area, the paper said.

The paper said Scheen and his two Congolese staff are now with U.N. peacekeepers and are doing well.

“We would like to thank everyone in Germany, Belgium and Congo who worked so hard in the past days to free Thomas Scheen, especially the German Foreign Ministry, the Belgian authorities and MONUC,” said the newspaper’s publisher, Berthold Kohler.

CNN.com