Catalan separatists burned barricades and clashed with police in Barcelona in a fourth night of violence triggered by Spain  jailing of nine of their leaders over a failed independence bid.

Hundreds of young protesters chanting “independence” set fire to improvised roadblocks in the center of the city late in the evening, tossing Molotov cocktails at police, who responded by firing foam and anti-riot rounds, according to sources.

The fresh clashes came on the eve of a huge protest planned in the Catalan capital.

Separatists have called a general strike and a rally on Friday against the Supreme Court’s decision to jail the separatist leaders for their role in a referendum banned by Madrid and a short-lived declaration of independence.

Earlier on Thursday, around 25,000 striking students and their supporters took part in a midday rally outside Barcelona city hall, according to municipal police.

Thousands more are on a cross-country march towards Barcelona for Friday’s rally.

After years of peaceful separatist demonstrations, violence finally exploded on the Catalan streets this week, led by activists frustrated by the political paralysis and infuriated by the Supreme Court’s conviction of nine of its leaders over a failed independence bid.

Since 2012, the independence camp has taken pride in its huge colorful marches of hundreds of thousands of people demonstrating their support for separation from Spain in a friendly, festival-like atmosphere.