Spanish police said on Thursday that they arrested eight demonstrators after violent clashes with protesters opposed to a visit by Pope Benedict XVI.
Eleven people were reported injured, including two police officers.
The violence broke out on Wednesday night as thousands of people gathered at Madrid’s Puerta del Sol.
They are angry that taxpayers’ money is being spent on the pontiff’s four-day trip at a time of severe economic crisis in Spain.
Benedict is in Madrid for World Youth Day, an event organised for young Catholics.
Its estimated price tag is at least 50-million euros.
Organisers say the arrival of hundreds of thousands of pilgrims will inject more than 100-million euros into the Spanish economy and cover the cost of the papal visit.