Foreign Minister Leonard She Okitundu signed for President Kabila

The agreement includes a new constitution and a power-sharing administration which is supposed to oversee DR Congo's first democratic elections since 1960 in two years' time.

However, President Joseph Kabila and MLC rebel leader Jean-Pierre Bemba did not personally sign the two page document.

Welcoming the deal, South Africa's President Mbeki warned of problems ahead from both within and outside the country's borders.

UN Secretary-General Kofi Annan said that the most difficult times lay ahead, saying: "No one must imagine that this deal will implement itself."

Graves

Ethnic conflict among militias in the north-eastern Ituri region, which has born the brunt of the violence in recent months, is still a major stumbling block to peace.

DR CONGO'S DEAL President Joseph Kabila stays Rebels and civilian opposition name vice presidents Elections in 2005 Factions integrated into new army A hard road to peace

Speaking from the regional capital, Bunia, the BBC's Mark Dummett says that worries remain because too many people still have guns and ethnic hatreds are not going away.

He told the BBC's Network Africa programme of the scene of utter devastation he witnessed on a 40km stretch of road out of Bunia, with fresh graves at the roadside and all the villages he passed through being burnt out.

Villagers in Kobo showed him what they said were several mass graves from the end of February that contained between 35 and 75 bodies in them.

As well as continuing ethnic conflict in the area, there is also growing tension between neighbouring Uganda and Rwanda over the refusal of Ugandan troops to pull out of Bunia.

DR Congo, Rwanda and Uganda all signed a deal to end the war last year but recently Rwanda threatened to send its troops back onto Congolese territory unless Uganda also withdraws.

Problems

The signing of the deal in the Sun City resort was witnessed by several regional leaders but questions still remain over the integrating of the different factions into a new army.

Rebel leaders are also unsure about their security in the capital, Kinshasa.

The signing endorsed an agreement last December and a new constitution reached last month.

Under the deal, President Kabila keeps his post, while rebels and the civilian opposition get vice-presidential posts in a two-year transitional authority.