Attitudes hardened at the start of a make-or-break week for Spain's deepest political crisis in decades, with firefighters, teachers and students also warning of strikes and protests.

Madrid stood firm on its plans to replace the government of the semi-autonomous region whose inhabitants voted "Yes" in a banned independence referendum on October 1.

Catalonia's separatist parties, in turn, called a special session of the regional parliament for Thursday to devise a response.

Observers fear this may amount to a unilateral declaration of independence that will spark unrest in the wealthy, northeastern territory and further afield.