African leaders witnessing the signing in the Tanzanian city of Dar es Salaam gave the smaller rebel National Liberation Forces (FNL) three months to open negotiations to reach a comprehensive peace accord for Burundi or face consequences.
Women and children danced and sang as Ndayizeye and Nkurunziza, the head of the Forces for the Defense of Democracy (FDD), signed the power-sharing accord.
The war, which erupted with the 1993 assassination of president Melchior Ndadaye, the country's first Hutu president, by the minority Tutsi-dominated army, has left some 300 000 people dead, mainly civilians.
The peace accord calls for power-sharing between Ndayizeye's government and the FDD and the rebels' integration into the Tutsi-dominated army.
The four African presidents and other top regional officials present at the signing called on the FNL "to immediately suspend hostilities and acts of violence and to participate in the negotiations with the government within a maximum of three months".
They added: "After this deadline, and in case of a categorical refusal to join the negotiation process, the Burundi people, the Regional Initiative on Burundi and the African Union will consider it to be an organisation that is against peace and stability in Burundi and will treat it as such".
The FNL only a week ago mounted a deadly attack on the capital Bujumbura, and at least 17 people have been killed in clashes between army forces and the FNL rebels.
On Saturday the rebels claimed to have killed nine soldiers near Bujumbura, where the army confirmed fighting but denied any of its men had been killed.
Attending the ceremony were Ugandan President Yoweri Museveni, who chairs a regional initiative on peace on Burundi and convened the summit, and Mozambique's President Joaquim Chissano, deputy chairperson of the initiative and chairperson of the African Union.
Also present were the chief mediator, South African Deputy President Jacob Zuma, and President Joseph Kabila of the Democratic Republic of Congo.
Tanzanian President Benjamin Mkapa, currently in Geneva for medical tests, was unable to host the summit and was represented by his vice president, Ali Mohammed Shein.
Gabon, Kenya and Zambia were also represented at vice presidential or ministerial level.
Before yesterday's signing a diplomat who requested anonymity said of the FNL: "The question is whether the heads of state will approve military action against them or try to bring them into the peace process. But in either case that will be difficult".
FDD secretary general Hussein Radjabu had on Saturday denounced the FNL for refusing to negotiate. "They are going to lose enormously. They fought, and did an admirable job, but they are not taking advantage of this opportunity," he said.
The Burundian president, for his part, urged the FNL to "stop exactions against the population and join without delay the negotiating table". – Sapa-AFP.