The 12 defendants are on trial for holding a banned referendum and later issuing a short-lived declaration of independence, with Spain's Supreme Court to issue its verdict later this month.
Their four-month trial, which began in February, was dismissed by separatists as a politically-motivated “farce” but was closely watched both at home and abroad.
Nine are charged with rebellion and if convicted, could face between seven and 25 years behind bars. Three others are accused of disobedience and misuse of public funds.
“A guilty verdict for the political and social representatives of the country (region) would constitute the biggest attack on our fundamental rights,” said former far-left separatist MP David Fernandez, reading out a joint statement by pro-independence parties and associations.
“We therefore… call on all citizens to respond en masse with non-violent struggle and peaceful civil disobedience,” it said.
Although there was no official plan laid out, several officials spoke about a strike, or marches aimed at blocking regional roads.
A region divided
The statement was issued on the anniversary of the referendum of October 1st, 2017, when police violently cracked down on would-be voters as regional leaders pushed ahead with a ballot that Madrid had declared illegal.
Four weeks later, on October 27, Catalan lawmakers narrowly approved a motion to declare an independent republic, sparking an immediate backlash from the central government in Madrid.
Sacking the Catalan government, Madrid imposed direct control over the region, prompting its leader Carles Puigdemont to flee to Belgium while others were rounded up and jailed.
Although the secessionists remain in power in this wealthy northeastern region, its leaders remain divided over how to achieve independence.
And with the verdict looming, tensions have mounted.
Last week, pro-independence parties adopted a clutch of controversial motions granting legitimacy to “civil disobedience”, demanding the withdrawal of Spain's national police, and calling for an amnesty for the jailed leaders.
The move came on the same day that police charged seven Catalan separatists suspected of preparing violent attacks with belonging to a “terrorist organisation”.
The use of violence during the 2017 crisis has been at the heart of the case against nine of the 12 jailed leaders because it is a key element of the charge of rebellion that they are facing, which carries a very heavy penalty.
The separatists have always stressed the peaceful nature of their movement, but the region remains divided over the question of separating from Spain, with a poll last month showing 44 percent in favour but 48.3 percent against