NICOLA Sturgeon said she is "appalled" by the decision of Spain's Supreme Court to convict Catalan politicians and activists following their bid to win independence in 2017.

In a verdict given by the court today, nine separatist leaders were handed prison sentences of between nine to 13 years for their roles in the move to secede.

Three other defendants were found guilty of disobedience and fined but will not serve prison sentences.

READ MORE: 100 years of jail time for pro-independence Catalan leaders

Scotland's First Minister said that the future of Catalonia should be decided at the ballot box, not in the courts.

"I am appalled by today's outcome," said Sturgeon in reaction to the judgment.

"These politicians have been jailed for seeking to allow the people of Catalonia to peacefully choose their own future. Any political system that leads to such a dreadful outcome needs urgent change.

"The future of Catalonia should be decided through the ballot box, not in the courts."

The First Minister added: "While it is not for us to take a view on the future of Catalonia, we do have a view on the upholding of democratic expression and civil rights and have a duty to speak up whenever and wherever those rights are under attack.

"Our thoughts and solidarity are with those sentenced today and their families.

"We will continue to encourage the Spanish and Catalan Governments to resolve their differences by mutually agreed democratic means."

READ MORE: Europe, now it's up to you: Full statement from Catalonia’s Foreign Minister

Pro-independence protesters have massed at Barcelona’s airport, with reports demonstrators have cut off rail and road links in other parts of Catalonia.

Police have since launched an operation to clear protesters from the airport.

SNP MEP Alyn Smith said that the EU could be doing more to help facilitate a "respectful discussion" on the future of the region.

The National:

He said: "I have to make a point today of all days in terms of Catalonia and the judgments which have been made from the Spanish judiciary in respect of the Catalan pro-independence leaders receiving some dreadful, appallingly unjust sentences.

"It is a European significant level discussion. We have one group of people in Catalonia, and remember the pro-independence side of Catalonia don't speak for all Catalans, not by a country mile do they.

"But you've got one group of people trying to use democracy to override the rule of law and you've got another side of people trying to use the rule of law to override democracy.

"Neither works and we, as friendly outsiders to both the state of Spain and Catalonia, we support the right to self-determination, we also support the rule of law.

"And the EU could be doing an awful lot more to facilitate a respectful discussion than it has done and it is not good enough that the EU has not stepped up to that mark.

"For my part, I'll keep the pressure up with colleagues to take it in that direction."