Despite calls from Catalan politicians to condemn the police violence on Sunday (1 October) against voters in the independence referendum across Catalonia, the EU has remained silent, deeming the issue an internal Spanish matter.

Over 800 people were injured, according to Catalan authorities, in a brutal police crackdown at polling stations in the referendum that was ruled illegal by Spain's Constitutional Court.

Belgium's premier broke the silence of EU leaders on Sunday. Charles Michel tweeted: "Violence can never be the answer! We condemn all forms of violence and reaffirm our call for political dialogue."

Belgium has its own separatist movement in its Flemish region, headed by the country's largest party, the New Flemish Alliance (N-VA), which is currently participating in Michel's government.

N-VA leader Bart De Wever tweeted simultaneously with Michel, warning: "[There is] no place in Europe for politicians who use violence. Whoever keeps refusing a call for international mediation, is ignoring democracy."

Slovenia's prime minister, Miro Cerar, also spoke out, tweeting: "I am concerned about the situation. I call for political dialogue, rule of law and peaceful solutions."

British foreign secretary Boris Johnson expressed "worry" over the violence, but recalled that the vote was ruled unconstitutional. "We are obviously worried by any violence, but clearly the referendum, as I understand it, is not constitutional, so a balance needs to be struck," he told Reuters.

The Lithuanian foreign minister, Linas Linkevicius, said in a tweet: "Emotional charge is strong, wounds of mistrust deep, dialogue with own people is a must for Spain. Violence will not help."

Scotland's prime minister, who has been arguing for a second Scottish independence referendum after voters chose in 2014 to remain part of the UK, also expressed concern over the violence.

"Increasingly concerned by images from Catalonia. Regardless of views on independence, we should all condemn the scenes being witnessed," Nicola Sturgeon said on Twitter.

Germany's chancellor, Angela Merkel, reportedly called her Spanish counterpart, Mariano Rajoy, for updates on the situation on Sunday, but made no statement.

Merkel and Rajoy both belong to the largest political family in Europe, the conservative European People's Party (EPP), which also remained silent on Sunday.

The centre-left Socialist and the Democrats group in the European Parliament put out a carefully balanced statement, saying "the solution can only be a political response, not a police one."

Former Belgian prime minister and leader of the liberal group (Alde), Guy Verhofstadt, also said that he did "not want to interfere" in Spain's domestic affairs, but added that it was "high time for de-escalation". "I absolutely condemn what happened today in Catalonia," he added.

With a plenary week starting on Monday in the European Parliament, the Greens have been calling for a debate on the situation on Catalonia. It will be up to the majority of MEPs present to give the go ahead.

The European Commission also remained silent. The EU executive has so far refused to comment substantially on the Catalan referendum, saying it respects the legal and constitutional order of EU member states.

It has also refused to say, in recent days, whether it would accept a role as a mediator between Spanish and Catalan authorities.

Catalonia's leader, Carles Puigdemont, said on Sunday that the EU cannot continue to look the other way.

"We are European citizens and our rights and freedoms are being violated," he was quoted by AFP as saying.

The situation in Catalonia "is a matter of European interest," he added.

The EU has been facing a dilemma with Catalonia.

Some EU countries fear separatist movements on their own turf, and the EU fears being seen as encouraging secession movements in any of its member state.

However, the police crackdown puts the EU in the spotlight. It makes it difficult to stand up for the rule of law when it has been enforced by Spanish authorities violently attacking peaceful voters - even if the referendum itself had been deemed unconstitutional.