Catalan leaders, both for and against independence, called on the European Commission Thursday to mediate in the standoff between Catalonia and Madrid over the regional government’s plan to hold a referendum on breaking away from Spain.

Raül Romeva, foreign secretary for the pro-independence regional government, told a press briefing in Brussels that the Commission “must defend the Treaty of the European Union and stand for the general interest of Catalan citizens as the EU citizens they are.”

The Spanish government has adopted a range of measures — including police raids, arrests and confiscation of ballots — to prevent the Catalan government from holding an independence referendum on Sunday. Madrid, backed by Spain’s constitutional court, says the referendum is illegal. The Catalan government says the vote is a legitimate act of self-determination.

“The European Commission can no longer argue that this is a domestic issue,” Romeva declared.

Barcelona Mayor Ada Colau, who is against secession but supports a referendum, called on the EU to “defend the fundamental rights of Catalan citizens against a wave of repression from the Spanish state.”

Writing in the Guardian’s Thursday edition, Colau said: “Europe cannot allow itself to adopt a passive position over the Catalan question, seeing that the events going on in Barcelona are affecting Paris, Madrid, Brussels, and Berlin alike.”

Colau wrote that many like herself are “calling for a negotiated solution in accordance with the feelings of 82 percent of the Catalan population who support the holding of an agreed referendum.” That was a reference to a poll in El País this week showing that a wide majority of people in Catalonia want a referendum on the issue — although the poll specified that they favored a legal plebiscite, agreed with Madrid.

Colau said the Spanish government has proved “itself incapable of finding a solution” to the dispute, prompting her call for the EU to step in.

In Brussels, Romeva referred to Commission President Jean-Claude Juncker’s statement that he wants the Commission to be “big on big things and small on small things.”

“The point here is that what we have in Catalonia is by far not a small thing, it is a big thing and needs to be dealt in a big way,” he said.

Juncker caused confusion earlier this month when he said the Commission respected the decisions of the Spanish government and constitutional court but also said “if there would be a Yes vote in favor of Catalan independence, then we will respect that opinion.” The Commission later clarified that Jucker was talking about a hypothetical legal referendum at some future point.

“The president said that the decision of the Spanish constitutional court needs to be respected and hence a referendum outcome can only be accepted if this condition is met,” a Commission spokesperson said.

This article has been updated.