SAO PAULO, Brazil — On Thursday morning, while the world’s eyes were focused on the Arena de Sao Paulo, where Brazil would later beat Croatia in the opening game of the World Cup, a few kilometers away protesters were locked in street battles with platoons of riot police.

The protests were the latest manifestation of a movement that has been building for a year: Brazilians angry about government waste and spending on the World Cup have been in the streets since last June, when Brazil saw its biggest demonstrations in decades.

The police fired stun grenades and tear gas into the crowd of mostly young militant protesters, pushing them from neighborhood to neighborhood and leaving a trail of injuries and chaos in their wake.