"If the yes wins, if the no wins - in any scenario there must be mediation because things aren't working", he told AFP.
"We don't know what is going to happen tomorrow".
A Spanish government source said more than half the schools had been closed off and police would remove people who attempted to vote on Sunday.
And on Friday, as children finished their school day, parents, kids, teachers and activists rushed to occupy building designated as polling stations to stop police from closing them. The region has its own language and culture as well as a notable amount of autonomy from Spain's central government in Madrid, but Catalonia is not recognized as its own nation under the Spanish constitution.
"I think that from now it would be logical for the European Union to actively monitor [the situation] and actively take an interest", he said.
Public support for the referendum within Catalonia, a wealthy region in Spain's northeast, has become increasingly vocal as the vote has neared.
The vote is scheduled to proceed despite fierce opposition from Madrid, including seizure of millions of ballot papers, arrests of Catalan election officials, censorship of referendum websites, and heavy daily fines for election board members as long as the vote moves forward.
Parents supporting the ballot across the north-eastern region arranged to occupy schools throughout the weekend so they can be used as polling stations.
The Catalan government said police have settled into its communications hub and will remain there for the next two days after it was ordered by Catalonia's High Court to police to stop electronic voting.
While the issue has been disputed for years, many Canadians are still wondering how the Catalan independence movement came to be, and what implications it could hold for Europe. The court also ordered Google to eliminate an application created to help Catalans identify polling stations.
On Saturday, Guardia Civil officers raided the Catalan government's telecommunications and information technology center, Joan Maria Piqué, the global communications director for the government of Catalonia, told CNN.
How the 17,000 Catalan regional police respond to this order is regarded as key to the success or failure of the planned vote.
The situation in Sortidor square was similar to the one in Collaso I Gil school in Barcelona, whose entrance was decorated with a poster that read "Defend this voting station".
Organisers said 60,000 people had registered to participate in the mass school sleepover which they say will show "peaceful resistance", even if they are prevented from voting. Many complain that Catalonia ends up subsidizing other parts of Spain.
And despite the passions provoked on both sides, there has been no violence nor calls to violence, but the tension has turned Catalan independence into a powder keg in Western Europe.