FORTALEZA: Brazilian police clashed with protesters Thursday ahead of a Confederations Cup semi-final, as President Dilma Rousseff's allies backed her plans for a plebiscite on political reform aimed at defusing public anger.

A wave of nationwide mass demonstrations, which began more than two weeks ago against a backdrop of anemic economic growth and rising inflation, have coincided with the Confederations Cup, a dry run for the 2014 World Cup.

Protesters are clamoring for better public services and tougher penalties against corrupt politicians, and are angry over the billions of dollars being spent to host the two high-profile football tournaments and the 2016 Summer Olympics.

The death toll from the more than two weeks of protests rose to five Thursday, when a 21-year-old man died in hospital a day after he fell from an overpass during a demonstration in Belo Horizonte.

The demonstrations have tapered off in terms of size -- down from 1.2 million people that flooded the streets of Brazil's major cities one week ago -- but those demanding change are still turning out with great passion.

About 5,000 young demonstrators staged a peaceful march Thursday in the northeastern city of Fortaleza to the Castelao stadium, where Spain edged Italy 7-6 on penalties to book a place in Sunday's final against Brazil in Rio.

"We are not against (world's football governing body) FIFA or the World Cup, but we are against the huge investments made (for the event). Public health, education, and roads are in a sorry state, and politicians prefer to invest in football," said protester Teo Sucupira.

Police clashed with a small group of hard-core protesters that hurled stones and tried to remove metal barriers set up to block access to the stadium. Some protesters set tires ablaze.

Police said they arrested 84 people. At least five demonstrators and three police officers were injured in the confrontation, the G1 news website reported.

Another 5,000 people also took to the streets of downtown Rio de Janeiro, while in Porto Alegre protesters gathered to demand lower public transportation fares.