Separatists in Catalonia, north-eastern Spain, are gathering for a march in Barcelona in protest at the jailing of their leaders nearly two weeks ago.
Previous protests in the regional capital drew hundreds of thousands of supporters, but were marred by rioting which saw more than 600 people injured.
Organisers are calling for a peaceful march which will also underline support for self-determination.
Spanish unionists plan to hold their own mass rally in the city on Sunday.
The days that followed saw some of the worst violence in the history of the modern independence movement, which prides itself on its peaceful tactics.
What is happening on Saturday?
A day of protest in Barcelona began with a gathering of mayors from across Catalonia to endorse the campaign for self-determination.
Mayors of 814 out of the region’s 947 local authorities gathered at the regional government’s headquarters to meet Catalan President Quim Torra.
As the mayors chanted “independence”, Mr Torra said Catalans must unite to oppose “repression” and “force the Spanish state to talk”.
Grassroots independence groups are urging independence supporters to fill the streets but say they are committed to peaceful protests, Reuters news agency reports.
On Sunday, politicians from Spain’s two main centre-right parties, the Popular Party and Ciudadanos, are expected to attend the unionist rally, which comes two weeks before the Spanish general election.
Meanwhile, supporters of the far-right Vox party rallied in the Spanish capital Madrid on Saturday to hear calls for a harder line on the separatists.
Party leader Santiago Abascal attacked Spain’s mainstream parties, including the ruling Socialists, telling the crowd: “Faced with criminal separatism, there is only Vox!”
How bad were the clashes earlier this month?
Rioters threw paving stones and petrol bombs while police fired baton rounds and used truncheons.
Cars and other property were damaged as fires were lit in the streets of Barcelona and other towns.
Between 14 and 20 October, 593 people, including 226 police officers, received treatment for injuries as a result of the protests, according to regional emergency services.
The Spanish authorities later updated the number of officers injured to 289.
Why is there a crisis in Catalonia?
Successive Spanish governments have refused to grant separatists in Catalonia a referendum on independence, which became a live issue again after the global financial crisis of 2008.
Spurred on by the results of an unrecognised plebiscite in November 2014, separatists held an illegal referendum in October 2017, which Spain tried to prevent by force, eventually jailing the separatist leaders.
While the separatists regularly attract massive shows of public support, they have only a slim majority in the regional parliament and a recent survey suggests Catalonia’s residents oppose independence by about 48% to 44%.
Catalonia has its own language and distinctive traditions, and a population nearly as big as Switzerland’s (7.5 million). It is one of Spain’s wealthiest regions, making up 16% of the national population and accounting for almost 19% of Spanish GDP.
The EU has treated the crisis as an internal matter for Spain, deaf to the separatists’ pleas for support, but there have been warnings that the issue is damaging Spain’s democratic credentials.