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Barcelona erupted in protest on Monday after a ruling by Spain's Supreme Court. Nine separatist leaders in the country's Catalonia region were found guilty of sedition for their role in a 2017 independence referendum. The nine leaders have been in detention since the independence vote took place almost two years ago. Now they face between nine and 13 years in prison. Lucia Benavides reports from Barcelona.

LUCIA BENAVIDES, BYLINE: Thousands of pro-independence protesters gathered at Barcelona's airport Monday afternoon, calling for the liberty of jailed Catalan separatist leaders. Police cut off train and metro lines to the airport after the first protesters arrived. But hundreds more joined by walking nearly 7 miles down the highway and shutting down traffic.

Maria Massot was one of the protesters walking to the airport.

MARIA MASSOT: (Speaking Catalan).

BENAVIDES: "I have no words for this," she told me. "When I woke up this morning, I started crying from helplessness and anger."

In October 2017, the regional Catalan government held an independence referendum that was considered unconstitutional by Madrid. Nonetheless, the yes vote won with 90%. And after Catalonia declared independence, Spain quickly dismissed the move and arrested nine of its leaders. After a four-month trial that began in February, those leaders were handed down their prison sentences this morning.

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QUIM TORRA: And convicting them is an insult to democracy and a show of contempt for Catalan society.

BENAVIDES: That's Catalan President Quim Torra. His government released a statement calling for international players to get involved, saying nobody can remain silent before this violation of fundamental rights. Monday's protests resulted in more than a hundred flights being canceled out of Barcelona's airport.

For NPR News, I'm Lucia Benavides in Barcelona. Transcript provided by NPR, Copyright NPR.