All schools closed in the capital of Guinea-Bissau on Tuesday as teachers and pupils joined forces in a march for peace.
It was called as the country heads towards presidential elections fraught with tension and fears of violence.
The march from the outer suburbs of Bissau to the presidential palace was the biggest public demonstration seen in living memory in this former Portuguese colony of 1.3 million people.
Police and the organisers estimated that at least 15,000 people took part in the march. They carried banners proclaiming "We want peace for Guinea-Bissau."
The massive demonstration for peace passed off smoothly, unlike a much smaller rally later in the day by supporters of ousted president Kumba Yala, who is determined to make a comeback.
About 150 supporters of Yala, who was deposed in a bloodless coup in September 2003, gathered to demand his immediate reinstatement as head of state.
They were dispersed by police with tear gas while soldiers stood by and looked on impassively.
Yala is one of the leading contenders in presidential elections on 19 June which are due to complete this small West African country's return to democracy.
But political tension rose on Sunday when the ousted leader announced that he was withdrawing his resignation as president, which had been forced upon him by the army, and was reclaiming his position as head of state with immediate effect.
The government of Prime Minister Carlos Gomes Junior, which came to power following parliamentary elections last year, ignored this statement.
But Defence Minister Martinho Ndafa Kabi held hurried consultations with military chiefs on Monday and announced afterwards that the army continued to fully support the government and the agreed process of transition back to constitutional rule.
Yala, whose three years in power brought administrative chaos and near bankruptcy to Guinea-Bissau, has been chosen as the presidential candidate of his Social Renovation Party (PRS), which is now the main opposition party in parliament.
The PRS draws heavy support from Yala's Balanta ethnic group. This accounts for one third of Guinea-Bissau's population and provides 90 percent of the soliders in the army.
Interim President Rosa urged the peace demonstrators who converged on his palace to stay calm and he reminded the armed forces of their duty to defend democracy.
"I ask all Guineans to remain calm and serene. Do not abandon your homes and jobs and the normality of everyday life," Rosa said in a speech to the demonstrators. "We must all remain alert and vigilant to protect the democratic order of Guinea-Bissau and the civic liberty of its citizens."
Turning to the security forces, Rosa said: "The revolutionary armed forces of our people and the forces of security and public order must hark to their responsibility and stick to their role in this process, remaining faithful to the flag of the republic, protecting freedom and defending the constitution and laws of the nation."
Rosa, a respected businessman who was charged with running Guinea-Bissau's first multi-party elections in 1994, said he was determined to stick with the democratic transition process "until the end."
Yala's main rivals in next month's presidential election will be Malam Bacai Sanha, the official candidate of the ruling African Party for the Independence of Guinea Bissau and Cape Verde (PAIGC), and Joao Bernardo "Nino" Vieira, a former military strongman, who ruled the country for 19 years until he was ousted from power in a 1998-1999 civil war.
Vieira, like Yala, is a controversial figure, who for many brings bitter memories of a conflict-ridden past.
His participation in the election is particularly unwelcome to the government since he is likely to split the vote of the ruling PAIGC, in which he still has many powerful supporters.
Vieira has lived in exile in Portugal for the past six years.
He returned briefly in April to register for the presidential election, but has not yet come home definitively to launch his election campaign.
The United Nations has expressed concern at the rising tension in Guinea-Bissau ahead of the presidential election.
UN Secretary General Kofi Annan reacted to Yala's demand for his immediate reinstatement as head of state by calling on "all segments of Bissau Guinean society, in particular political leaders, to desist from any actions or statement that could undermine peaceful and orderly electoral and transitional processes."