BRUSSELS (Reuters) - The premier of Belgium's Flanders region, which has itself seen separatist frictions in the past, denounced Spanish authorities on Friday for arresting sacked separatist Catalan officials and urged the EU to mediate in the dispute.

Carles Puigdemont, dismissed by Madrid as Catalan leader after the region's unilateral declaration of independence, travelled to Belgium and failed to appear in a Spanish court on Thursday to answer charges of rebellion. But nine associates were remanded in custody in Madrid pending possible trial.

"Locking up democratically elected leaders is more than a bridge too far," Flanders premier Geert Bourgeois said in a statement.


"I'm perplexed that something like that is possible in today's Europe."

Flanders, home to more than half of Belgium's inhabitants, has also seen separatist campaigning in past decades but a series of constitutional reviews has given broad autonomy to the regions and kept a lid on tensions.

Bourgeois, of Flemish nationalist party N-VA which is also part of Belgium's federal government, called on European institutions to mediate; a proposal it has already rejected.

"Once again I'm urgently calling on all European entities to finally take action and look for democratic solutions with both Spain and Catalonia," he added.

The European Commission reiterated on Friday it fully respected Spain's internal political and judicial order.

(Reporting by Robert-Jan Bartunek; editing by Ralph Boulton)