The transitional administration composed of once bitterest enemies should pave the way for the country's first democratic elections in two years' time, if all goes according to plan.

The five-year war has been described as the worst conflict since World War II involving tens of thousands of foreign troops and resulting in the estimated deaths of at some three million people.

Residents in Kinshasa have mixed feelings about the deal, with one woman telling the BBC: "Most of the time we see politicians take decisions today, then tomorrow they change."

Another said he was happy: "If the country is united then there's no problem, the government can go on."

The ceremony formally spells the end of the war, but the BBC's Ishbel Matheson says there are many obstacles to be overcome.

One possible problem for the new government is the absence so far of an agreement on how rebel and government forces might be integrated in a new national army.

Another is continuing conflict in eastern Ituri province which is in a state of anarchy with numerous ethnic militias committing terrible human rights abuses such as rape, murder and cannibalism, our correspondent says.

The latest accusation of a brutal attack comes from a local militia leader in Bunia who accused government allied militias of launching a raid on a hospital in the village of Tchomia on Wednesday killing 47 people.

The leader of the largest rebel group arrived in Kinshasa on Wednesday, ending days of speculation about whether he would take up his seat in the transitional government, after disputes over security arrangements and the sharing of control of the DR Congo's military districts.

Speaking to reporters, Azarias Ruberwa, leader of the Rwanda-backed Congolese Rally for Democracy-Goma (RCD-Goma) said: "Our arrival marks the effective start of the transition."

"We have already announced the end of the war, now it's a reality."