Spain's Supreme Court is expected to announce on Monday its highly anticipated verdict in the trial of 12 Catalan separatist leaders over their role in the region's 2017 banned referendum and short-lived independence declaration.

Much is at stake, both for Spain and for its wealthiest region in this trial over a failed independence bid that attracted worldwide attention, triggered Spain's biggest political crisis in decades and unnerved financial markets.

Secessionist groups have called for massive but peaceful civil disobedience if the 12 — nine of them have been in pre-trial detention for close to two years — are not acquitted.