It is the first time that the Bujumbura government, drawn largely from the ranks of the Tutsi minority, and the main rebel group, from the Hutu majority, have signed such a pact since the country's civil war began in 1993.

The fighting has pitted the largely Tutsi army against a range of Hutu rebel groups. Most of the victims of the conflict have been civilians.

"The transitional government of Burundi and CNDD-FDD (rebels) agreed to a ceasefire with effect from the date of the signature of the ceasefire agreement," a joint statement issued by the mediators stated.

However, responding to a question on this effective date of this ceasefire, President Yoweri Museveni said "it will start on December 30, taking into account preparation needed" by the two parties.

Museveni, who chairs the regional initiative for peace in Burundi, and head mediator South African Deputy President Jacob Zuma also signed the document.

Zuma told reporters that the "people who have signed a ceasefire agreement have indicated they will stop fighting immediately".

Ambroise Niyonsaba, the main negotiator on the government side, said: "Within 72 hours there will be a cessation of hostilities," while admitting that some aspects of the ceasefire would take longer to apply.

"We will study the political questions within 30 days," he told AFP. These details include how the FDD will participate in a government of transition under the terms of an earlier peace deal signed in August 2000 between the government and Hutu and Tutsi political parties but not the main rebel movements.

FDD rebel spokesman Gelase-Daniel Ndabirabe assured that "there will be no fighting from Tuesday," adding that negotiations would continue "to put in place the new transitional institutions".

President Buyoya hailed the signing of the ceasefire accord as "an important step but it is not the end. The process will continue towards applying the (2000) Arusha accord in its entirety and the application of the ceasefire".

Rebel leader Nkurunziza promised to respect the terms of the agreement "and I dare say that no one will go back on their word".

The historic signing came at the end of a two-day summit of regional heads of state dedicated to the situation in Burundi.

It had been delayed on Monday afternoon when rebel representatives complained that the drafts presented to them differed from the negotiated ones. The final signing went ahead some hours later.

The peace talks between the government in the small poverty-stricken central African state and Hutu rebels began in August, with both sides digging in their heels for a satisfactory settlement.

A previous round of talks between the two parties ended in deadlock on November 7 despite a threat by the regional leaders to take unspecified "appropriate measures" against both parties if they remained "recalcitrant".

The UN World Food Programme (WFP) meanwhile warned on Monday that more than a million Burundians were threatened by worsening food shortages.

More than 300,000 people have been killed in Burundi's civil war.

Also attending the summit here were presidents Thabo Mbeki of South Africa and Benjamin Mkapa of Tanzania, and Ethiopia's Prime Minister Meles Zenawi.

Kenya's President Daniel arap Moi sent Agriculture Minister Bonaya Godana, while Democratic Republic of Congo (DRC) President Joseph Kabila sent Information Minister Kikaya bin Kirumbi.

Gabon, the United Nations and the African Union also sent representatives.

SPACE.WIRE