Police in Barcelona faced further demonstrations last night as protests continued over the sentencing of nine leaders of the Catalan independence movement to lengthy prison terms.

Organisers of the protests, the authorities and the jailed independence campaigners alike called for calm after two days of often violent clashes.

Thousands joined marches setting off from five towns in Catalonia yesterday en route to the Catalan capital Barcelona, where they are due to arrive on Friday, triggering a planned general strike.

Organisers claimed the marches from Girona, Vic, Berga, Tarrega and Tarragona were 100 kilometers long, and while the size is disputed, the marchers b succeeded in blocking traffic across the region.

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The marches marked the third day of reactions, both peaceful and violent, to the prison sentences handed down to independence leaders, after they were found guilty of sedition for promoting the failed 2017 secession attempt by Catalonia’s regional government.

After the announcement on Monday, flights were cancelled and thousands of travellers stranded after protesters attempted to shut down Barcelona Airport. This was followed by violent clashes between police and demonstrators on Tuesday night.

Ahead of another big planned demonstration last night, organisers urged marchers to keep protests peaceful.

The nine Catalan leaders sentenced over a failed 2017 secession attempt by Catalonia’s regional government, also appealed for calm. “All support to mobilisations and massive and peaceful marches,” they wrote on social media. “No violence represents us.” They include former regional vice-president Oriol Junqueras and two prominent grassroots leaders, Jordi Sànchez and Jordi Cuixart. Four of the group were additionally convicted of misuse of public funds. The other three were fined for disobedience.

As well as the mass marches, yesterday also saw the start of a student strike and the interruption of services on the high-speed rail line between Barcelona and Girona, which the Spanish government blamed on “sabotage”.

As last night’s demonstration loomed, authorities in Barcelona were still attempting to clear up after Tuesday’s clashes. Debris from more than 150 barricades set up and then set alight by protesters had to be cleared away.

Police said 40,000 people had taken part in the protests in Barcelona packing the streets near the office of the Spanish government’s representative, as scuffles and running fights broke out. Outnumbered police face were targeted with missiles including rocks, firecracker and other objects, and retaliated using foam bullets, batons and shields.

A demonstration in Girona attracted a further 9,000 people, police said. Health authorities say they treated 125 people, both police and protesters. Police made 29 arrests in Barcelona, while similar protests turned toward violence in other towns in Catalonia.

Roughly half of Catalonia’s 7.5 million residents support independence, with the other half opposing a breakaway, according to polls. Spain’s acting prime minister Pedro Sanchez, who will seek re-election in a national election on November 10, said he is planning to meet with the leaders of the main opposition parties on Wednesday to discuss the situation in Catalonia.

“(I want to issue) my firmest and complete condemnation of the violence that is trying to shatter the social harmony in Catalonia,” Mr Sanchez wrote on Twitter. “All support for the forces of security.”

Gabriel Rufian, a leading Catalan separatist and member of Spain’s Parliament, and some other high-profile secessionists called for calm. “Nothing can justify violence,” Mr Rufian told Cadena SER radio.

Foment de Treball, which represents leading employers in Catalonia, also called for “calmness and serenity” and warned of a risk to economic activity through continued instability. In a statement, the organisation said: “Legitimate protest and freedom of expression” were no justification for violent actions that could have serious consequences for social cohesion.

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Critics claimed Catalonia’s regional president Quim Torra, who has called for a fresh vote on Catalan independence, had failed to specifically denounce the street violence.

Spanish Government spokeswoman Isabel Celaa said: “All our respect for those who peacefully protest, but not for those who interrupt transit or carried out the violent attacks. I urge president Torra to condemn the episode we saw yesterday.”

However last night Mr Torra after saying he was proud of the protesters and supported civil disobedience, added: “Violence does not represent us and will never represent the Catalan independence movement.”