"I'm calling on the sensible people in the Catalan government.don't jump off the edge because you'll take the people with you", Spanish Deputy Prime Minister Soraya Saenz de Santamara said.
Catalan leader Carles Puigdemont is due to address the regional parliament on Tuesday and the Madrid government is anxious it will vote for a unilateral declaration of independence.
On the eve of Sunday's rally, Spain's Prime Minister Mariano Rajoy refused to rule out suspending Catalonia's regional autonomy - a move that risks further unrest.
The address could be the moment when Catalonia's leader declares that the region will break away.
Some separatist politicians say Carles Puigdemont has no other choice but to make a declaration of independence for the wealthy northeastern region, which has a population of 7.5 million people.
"The exit of many companies from Catalonia is the effect of the irrational and radical policies implemented and pursued by the (regional) government", minister Luis de Guindos said as he arrived for a meeting of euro zone finance ministers in Luxembourg.
In an interview with the French TV station CNews, Nathalie Loiseau, France's minister of European affairs, said any declaration of independence would leave Catalonia isolated.
Recent opinion polls indicate that Catalans are split on independence, although regional leaders said police violence during the referendum turned many against Madrid.
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She said she was devastated by the carnage and would cooperate with authorities as they struggle to get inside Paddock's mind. In this frame grab, Las Vegas Metropolitan Police update onm shooter's timeline of events on October 4, 2017 in Las Vegas.
"Spain will not be divided and the national unity will be preserved".
Barcelona Mayor Ada Colau, however, urged the government to refrain from invoking the never-before-used Article 155, which allows Madrid to take over autonomous regions.
IG analyst Chris Beauchamp says a positive beginning of the week for the Spanish Ibex 35 index suggests investors are confident there will be a resolution to the crisis.
France, on the other hand, said that they will not be recognizing Catalonia should it declare its independence on Tuesday.
According to the Catalan government, a majority of those who took part in the illegal referendum voted for the separation of the region from Spain.
"Many people stayed home and didn't vote (Sunday) so the whole question of the mandate that he would have in speaking before that Parliament and declaring independence would be challenged".
Meanwhile, Nils Muizneks, the Human Rights Commissioner of the Council of Europe, revealed that he has requested Spain's Ministry of the Interior set up an independent enquiry into multiple claims of disproportionate use of excessive force by the Spanish police during the banned referendum on 1 October.
But Rajoy assured Catalan leaders that there "is still time" to backtrack and avoid the imposition of direct rule.
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