The day had started peacefully, with the city's streets turned into a sea of flags as a tide of humanity flowed down the wide avenue running from the waterfront to the city's towering Sagrada Familia basilica.
Catalan leaders demand talks with Madrid as thousands protest again
On an unseasonably warm October afternoon, the masses waved flags, sang songs and chanted slogans, among them many youngsters, elderly people and families with children.
But as night fell, thousands joined a separate demonstration by the radical CDR, massing outside police headquarters on Via Laeitana shouting "Occupation forces, out!" and hurling coloured plastic balls and marbles at the riot police guarding the building.
Although police initially refused to engage, they eventually charged, using batons and foam rounds to try and break up the crowds who pelted them with bottles, rocks and fireworks, an AFP correspondent said.
Police said around 10,000 demonstrators had massed in the street, which was eventually cleared by about 11:00 pm.
Catalonia has been gripped by unrest since the October 14 Supreme Court verdict which unleashed a wave of protest that quickly turned violent, with masked demonstrators clashing nightly with riot police.
More than 600 people have been injured in the protests, 367 of them civilians and 289 police, official figures show.
The crisis began two years ago when the region staged a banned referendum on October 1 that was marred by police violence, then issued a short-lived declaration of independence, trigging Spain's worst political crisis in decades.
Saturday's main rally was called by the ANC and Omnium Cultural, the region's two biggest grassroots pro-independence groups that have organised the largest separatist protests in recent years.
Marching down the spacious boulevard, demonstrators chanted "October 1, we won't forgive, we won't forget", breaking into loud boos and whistling as a police helicopter flew overhead.
"I feel really angry," said computer technician Marc, 26, who did not give his surname.
"The violence doesn't sit well with me but it's normal to have a bit of upheaval like we've seen in Chile and Ecuador," he said of a wave of mass protests in Latin America.
"There are different ways of protesting but we have one objective: independence."
Catalans remain sharply divided over the question of separating from Spain, with polls showing 44 per cent in favour and 48.3 per cent against.
Speaking to reporters at the rally, Catalonia's separatist president Quim Torra said his government was with the people "because it is what they want.
"We will go as far as they want".
He had earlier pledged to push ahead with the controversial independence drive after meeting 800 local mayors who expressed support for secession.
"The show of unity we've seen this week shows the next step that we all must follow... We must all push ahead and exercise the right to self-determination."
Torra has made repeated appeals for dialogue with the Socialist government of Pedro Sanchez with the aim of securing Madrid's agreement for a referendum on independence, but they have fallen on deaf ears.
"What we will not talk about is the right to self-determination," Carmen Calvo, Sanchez's deputy, told journalists on Saturday.
"If.. the aim is to break up Spain's territorial unity and separate Catalonia from Spain, we simply cannot talk," she said.
"Unilaterally breaking the rules of the game is not an option."
On Sunday, Catalans who want to remain part of Spain are planning a massive counter-demonstration to raise the voice of the region's so-called "silent majority".
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"Those who oppose independence are a majority," said Fernando Sanchez Costa, head of Catalan Civil Society (SCC), telling AFP the unrest was causing a lot of damage to Catalan society.
Earlier, some 20,000 people gathered in Madrid in defence of Spain's unity, national police said, for a rally organised by the far-right Vox party, which has taken a very tough line on Catalan separatism and wants all regional pro-independence parties banned.
Although the faction only entered parliament in April, polls indicate it might become the third-largest party following the November 10 election.
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