Thousands of Catalan independence supporters, many wearing yellow ribbons in a show of unity, filled the enormous Avenue Marina in the city centre as they called for the seaports leader to be freed.
At sunset, many shone their mobile phone torches and aves their iconic Catalan flags in unison as the jailed leaders’ families gave speeches.
One protestor, 63-year-old Pep Morales, said: “Look at all the people here! The independence movement is still going strong.”
The protest is seen as a test of how the independence movement’s support has fared since the Catalan government declared independence on October 27, which prompted Spanish prime minister Mariano Rajoy to fire its members, dissolve the regional parliament and call new elections for December.
An opinion poll lent further evidence of the support for independence with separatist parties projected to win the largest share of the vote.
However, with disputed Catalan president Carles Puigdemont in still Belgium under self-imposed exile, questions about the future of the wealthy region remain unanswered.
He appears to still be popular in Catalonia, with chants of “Puigdemont for president” echoing around Barcelona as people played music and sang in the streets.
Protesters marched behind a banner declaring “We are a republic” and carried placards declaring the 10 detainees political prisoners.
On Thursday, the Supreme Court ruled to release on bail the Catalan parliament’s speaker Carme Forcadell and four other lawmakers, who enabled the declaration of independence by overseeing a parliamentary vote.
Forcadell left jail on Friday after agreeing to renounce any political activity that went against the Spanish constitution, in effect banning her from campaigning for independence in the December election.
Those terms threaten to undermine the independence movement just as cracks are starting to appear and tensions rise between the grassroots and their leaders.
Some of the imprisoned leaders are planning to stand in next month’s regional elections.
Puigdemont’s PDeCAT party has failed to agree on a united ticket to contest the election with another secessionist party, the ERC, denting the pro-independence camp’s hopes of pressing ahead after the election.
On Saturday, the ERC said its leader, jailed former Catalan vice-president Oriol Junqueras, would be its candidate in December and he would campaign from behind bars.
Pepita Sole, a 61-year-old pensioner in the crowd on Saturday, said she understood the October 27 independence declaration was symbolic but now wanted the real thing.
She warned: ”They better understand that we’re not faking.”