MADRID (AP) — European Commission President Jean-Claude Juncker says nationalist urges are “a poison” which harm the European Union’s efforts to speak with one voice on the world stage.

In what appeared to be indirect rebukes of an effort by some Catalan leaders to achieve their region’s independence from Spain, Juncker said during a trip to the Spanish city of Salamanca that nobody has the right to undo the EU’s model of coexistence.

Spain’s government dismissed Catalonia’s secession-minded Catalan government and dissolved the region’s parliament after bids to break away last month. Spain’s Constitution says the country is “indivisible,” and the national government deemed the secession attempts illegal.

In a speech in French upon receiving an honorary doctorate Thursday from Salamanca University, Juncker said, “yes to Europe, yes to its group of nations, yes to its regions, but no to breaking up along national and regional lines.”

Juncker noted that the EU is based on the rule of law, according to Spanish news agency Europa Press.