Riot policemen stand in position during an anti-World Cup protest on the morning the Brazilian mega-city hosts the tournament's opening match, in Sao Paulo on June 12, 2014
Police in Brazil arrested at least 18 people at anti-World Cup protests Saturday and broke up a group of rowdy Argentine fans with pepper spray in Rio de Janeiro.
At one protest in Belo Horizonte, the southeastern city that hosted Saturday's match between Colombia and Greece, police arrested 15 people carrying petrol bombs, knives, masks and bottles of vinegar, which demonstrators use to relieve the effects of tear gas, reported radio network CBN.
The group of about 200 people had been trying to march to the city's host stadium.
In the northeastern city of Fortaleza, around 100 protesters approached the stadium where Costa Rica were playing Uruguay.
Police arrested three of them, said news website G1.
Some 1,500 Argentina fans meanwhile partied on Rio de Janeiro's famous Copacabana beach ahead of their team's debut against Bosnia Sunday, G1 reported.
The fans blocked traffic at one point on beach side thoroughfare Atlantic Avenue, prompting police to use pepper spray to disperse them.
A Pope Francis impersonator could be seen at the Argentines' party, greeting revelers from a car and brandishing a replica World Cup trophy.
The real pope, an Argentine native, is a passionate football fan.
A year ago, hundreds of thousands of Brazilians took to the streets to protest the $11 billion being spent on the World Cup in a country that has pressing needs in health, education and transport.
Recent protests have been far smaller -- though sometimes more radical and violent.