CARACAS, Venezuela — Colombian President Uribe’s fight against the country’s biggest rebel group was strengthened yesterday as millions of Colombians marched nationwide to demand the end of the 44-year conflict and the release of all hostages.

Colombians flooded the streets in Bogota, Medellin, and Barranquilla for the “Great Mobilization for Freedom and Peace” march, on what is the 198th Colombian Independence Day, with concerts including a performance by the Colombian pop star Shakira. Recently liberated French-Colombia politician Ingrid Betancourt headed a gathering in Paris backed by Colombian musician Juanes in front of the Eiffel Tower, and similar marches took place in Caracas, Buenos Aires, and Miami.

Mr. Uribe, 56, in his sixth year of office, has dealt the Revolutionary Armed Forces of Colombia harsh blows in recent months, dismantling its leadership, turning commander against commander, and rescuing 15 of its most prized hostages. Still, as many as 700 captives remain in guerrilla hands and at least 8,000 guerrilla fighters still roam the jungles of Colombia, kidnapping and killing civilians and military personnel.

“Of course there’s a lot of euphoria,” the director at the Center for International Conflict Resolution at Columbia University in New York, Aldo Civico, said. “There’s a sense that we’re close to the end. The Colombia government is right now winning the military war, but the underlying causes of the conflict are still there.”

Twenty-one captives have been freed this year, after as much as a decade spent in jungle camps.

Mr. Uribe gathered yesterday alongside Brazil’s Luiz Inacio Lula da Silva, and Peru’s Alan Garcia in the jungle town of Leticia, along the 1,032-mile common border with Brazil. Saturday, Mr. Uribe agreed to form part of a South American defense council promoted by Brazil, after showing hesitation because of a lack of confidence in neighboring countries.