Spain's state prosecutor says he will seek charges of sedition and rebellion against ousted Catalan Cabinet officials.
Attorney General Jose Manuel Maza also called Monday for charges of embezzlement against Catalonia's leaders over their push to separate from Spain.
Catalonia's separatist party, however, announced it would run in an upcoming snap election in December, set up by the Spanish government after it dissolved the regional parliament.
Both announcements came as as Catalonia entered its first week after the Spanish central government's assertion of control over the would-be breakaway region.
There were no signs that now fired regional elected leaders, including the head of government, Carles Puigdemont, and other members of his deposed Cabinet would try to go to their offices Monday.
Puigdemont is likely to be accused of rebellion as early as Monday for pushing ahead with secession.
Sunday, hundreds of thousands of supporters of a united Spain took to the streets of Barcelona to voice their rejection of Catalonia’s declaration of independence.
Chanting "Viva Espana" and waving Spanish, Catalan and European Union flags, the protesters marched in Catalonia's capital to show they supported the Spanish central government's dismissal of Catalonia's cabinet and quashing of the region's secession push.
Protesters also held banners reading, “We won't let Spain be torn apart into pieces'' and ”The awakening of a silenced nation,'' among others.
“We have organized ourselves late, but we are here to show that there is a majority of Catalans that are no longer silent and that no longer want to be silenced,'' said Alex Ramos, head of the pro-union Catalan Civil Society.
Organizers said the rally attracted more than one million people, but police put the figure at 300,000.
Spanish Prime Minister Mariano Rajoy dissolved Catalonia's parliament, just hours after the regional body voted Friday in favor of independence from Spain.
In addition to dismissing the regional parliament, Rajoy has called for snap Catalan elections on December 21 and has stripped Catalonia's most senior police officials of their powers.
Spanish government spokesman Ínigo Mendez de Vigo has said Puigdemont and all other Catalonian leaders would be eligible to run in the December election.