There were arrests and injuries after Catalan separatists threw colored powder, ran at police lines and clashed with a pro-police rally. The Barcelona events came just days before the anniversary of the referendum.
Police in the Spanish region of Catalonia arrested six people on Saturday after violent scuffles between rival demonstrators in Barcelona left 14 people injured.
A rally of about 6,000 separatists obliged a rally of about 3,000 supporters of the national police to take another route through the city.
The police march was organized by the JUSAPOL police association, which wants Spain's national police and Civil Guard to be paid as much as Catalonia's regional police.
Tensions were running high ahead of the first anniversary of the independence referendum that had prompted a crackdown by Madrid.
Local Catalan police tried to keep the rival groups apart. Separatists threw colored powder which covered anti-riot police and their shields and vehicles.
When protesters approached the police lines they were kept back with batons.
The separatists chanted: "Neither forgetting nor forgiveness" and "Get out of here, fascists" to the union protesters waving Spanish flags in support of the national police on the main city square. It was then that the clashes broke out.
Barcelona Mayor Ada Colau called for calm and said later on Catalunya Radio: "This city has always defended that everyone can exercise their rights to free speech."
Marking a year since the referendum
On Monday, Catalonia will mark the first anniversary of the referendum which saw around 90-percent of participants vote for independence from Spain.
However, only about 42 percent of registered voters took part in the vote, and Madrid dismissed the plebiscite as illegal. Carles Puigdemont, the pro-independence leader who spearheaded the referendum, fled Spain to avoid arrest and is currently living in Belgium.
dj/jm (AP, Reuters, dpa)