Sunday's protests, which were called mostly via social media by a variety of groups, are seen as a barometer of popular discontent with President Dilma Rousseff. Her second term in office has been shaken by a snowballing corruption scandal involving politicians from her Workers' Party, as well as a spluttering economy, spiraling currency and rising inflation.

Thousands of people brandishing green and yellow Brazilian flags streamed onto Rio's Copacabana Beach, and smaller demonstrations were . . .