The European Commission says Sunday’s independence referendum in Catalonia was “not legal” but also called on the Spanish government to open dialogue.

A spokesman for the commission, the executive arm of the 28-nation EU, said Monday that “violence can never be an instrument in politics.”

The commission said in a Twitter message that “these are times for unity and stability, not divisiveness and fragmentation.”

The director of the OSCE Office for Democratic Institutions and Human Rights (ODIHR) Ingibjörg Sólrún Gísladóttir also called on the Spanish authorities to ensure respect for fundamental freedoms of peaceful assembly and expression,” in order to facilitate communication and employ “de-escalation measures to reduce tensions.”

“The Spanish authorities must ensure that police use force only when necessary and in strict adherence to the principle of proportionality,” she said.