The city has witnessed daily pro-secession protests since Oct. 14, when Spain's Supreme Court jailed nine politicians and activists for up to 13 years for their role in a failed independence bid in 2017.
With some demonstrations marred by violence, turnouts down and separatist parties divided over strategy, Assemblea Nacional Catalana (ANC) and Omnium Cultural hoped Saturday's march would refocus the secessionist camp's attention by drawing the largest crowd since the court verdicts were passed.
"From the street we will keep defending all the (people's) rights but from the institutions we need political answers," ANC leader Elisenda Paluzie told the gathering, pledging to organize more protests.
Local police said around 350,000 attended on Saturday, compared with a daily peak of some 500,000 at a protest on Oct. 18 and 600,000 at a march that took place on Catalonia's national day last month.
All those figures, however, represent only a small percentage of the region's 7.5 million population and its electorate is almost evenly split over the issue of independence.
Both ANC and Omnium Cultural eschew violence and their then leaders were among the nine jailed.
While their event passed peacefully, a tense standoff with security forces developed at an early evening protest organized outside Spanish police headquarters by CDR, a pro-independence pressure group. It favors direct action and has cut railtracks and roads as well as trying to storm the regional parliament.
That protest drew a crowd of several thousand who chanted for "the forces of occupation" to leave.
They included Manel, a 20 year-old student with his face obscured by a cloth who said he was among those who lit barricades during last week's unrest.
"We need a consistent protest: more streets and less parliamentary talk because that doesn't seem to work," he said. "If we halt the economy, the Spanish government would be obliged to talk."
'PRISON IS NOT THE ANSWER'
At the grassroots march, many carried Catalan pro-independence flags and banners bearing slogans that included: "Prison is not the answer," "Sit and talk" and "Freedom for political prisoners."
In the front row was regional government head Quim Torra, who earlier presided over a ceremony at which hundreds of Catalan mayors endorsed a document demanding self-determination.
"We have to be capable of creating a republic of free men and woman ... and overcoming the confrontational dynamic with a constructive one," he told them.
While not currently affiliated to any party, Torra belongs to the separatist political movement Junts per Catalunya. It has been in favor of maintaining confrontation with authorities in Madrid, while its leftist coalition partner Esquerra Republicana de Catalunya favors dialog.
One marcher, 63-year-old Maria Llopart, criticized the lack of unity between the two parties. "Everything looks very bad, we are not advancing," she said.
Francesc Dot, 65, said the nine leaders had been jailed in defense of "Spain's unity."
His wife, Maria Dolors Rustarazo, 63, said she should also be in prison because she voted in the 2017 referendum, which Spanish courts outlawed. "If (all separatist votes)... have to go to jail, we will go but I don't think we would all fit," she said.
She condemned last week's rioting, which had hurt the pro-independence movement, but had understanding for young protesters being "angry at the lack of democracy."
Torra called in an interview with Reuters this week for Madrid to open talks with a view to the region holding a second referendum.
Mainstream Spanish parties, including the minority Socialist government, have consistently rejected moves towards Catalan independence and all bar left-wing Podemos are opposed to any form of referendum.
They are now gearing up for a national election on Nov. 10.
Addressing a party rally in Tenerife on Saturday, acting Prime Minister Pedro Sanchez called last week's unrest in Barcelona "an attack ...on Catalan society."
Catalan supporters of continued unity with Spain will hold a rival rally in Barcelona on Sunday that the leaders of the country two main center-right parties, PP and Ciudadanos, are due to attend.