Cubans tied yellow ribbons to homes, trees and lampposts across the capital last week, in an organized mass campaign to press for the return of several espionage agents imprisoned in the United States on the 15th anniversary of their arrest.

By using a symbol with deeply held cultural significance for many Americans, the campaign aims to raise support for the so-called Cuban Five in the United States where the public is largely unaware of their case, even if it’s a daily cause celebre in Cuba.

‘‘The symbolism of the yellow ribbon has a strong impact in the mind of Americans. It is a message of love that appeals to emotions,’’ said Rene Gonzalez, the only one of the Cuban Five who has been released from prison.

‘‘We are trying to send a message that we are human too,’’ added Gonzalez, who has been heading the campaign.

The Five were arrested Sept. 12, 1998, and convicted three years later of spying on U.S. military installations in South Florida, as well as exile groups and politicians. Havana maintains that they were only monitoring militant exiles to prevent terror attacks in Cuba, and posed no threat to U.S. sovereignty.

Gonzalez was paroled in 2011 after serving most of his sentence. Earlier this year a U.S. judge allowed him to renounce his citizenship and return to Cuba. The other four remain in prison, with one set to walk free in February.

Thousands of ribbons could be seen around the Cuban capital Thursday, from government buildings to private homes and small businesses. A huge strip of yellow hung from the iconic lighthouse at El Morro fortress at the mouth of Havana Bay. Many people wore yellow clothing, and young schoolgirls fixed yellow ribbons in their hair.

Students held a demonstration on the steps of the University of Havana, and Cuba’s association of artists and intellectuals marched from its headquarters to the U.S. Interests Section along the Malecon seafront boulevard.