Catalan separatists have clashed with police today as hundreds of thousands of pro-independence supporters pour into Barcelona on a general strike.

As the angry demonstrations entered their fifth day, activists blocked a string of roads in the wealthy northeastern region, cutting off the main cross-border highway with France.

Workers were also downing tools in a mass show of dissent over Monday's Supreme Court verdict in which the separatist leaders were handed long jail terms over a banned referendum and an abortive independence declaration two years ago.

Police officers clash with Catalan demonstrators during Catalonia's general strike in Barcelona today

Hundreds of thousands are taking part in the strike and pouring into Barcelona following a week of unrest

The angry demonstrations are in their fifth day after separatist leaders were handed long jail terms on Monday

Police officers are hit by white paint as they observe protesters gathering in Barcelona today

Concerns over security amid the disruption have forced organisers to postpone next week's 'El Clásico' match between Real Madrid and F.C. Barcelona.

The league's organising body made an official request to the federation this week for the game to be rearranged, which was approved on Friday.

Barcelona and Madrid now have until Monday to decide on a new date for the match.

As well as the strike, several thousands of people were due to end a three-day march to Barcelona from five regional towns in another coordinated move aimed at causing chaos on roads and highways in a region that accounts for about a fifth of Spain's economic output.

It comes as fugitive ex-Catalan leader Carles Puigdemont handed himself in to Belgian justice authorities after Spain issued a new warrant for his arrest following the sentencing of 12 of his former colleagues.

Mr Puigdemont's office said that he, 'in the company of his lawyers, voluntarily appeared before Belgian authorities' in relation to the arrest warrant.

It said Mr Puigdemont rejects the warrant and opposes any attempt to send him back to Spain.

Dozens have been injured in the clashes this week which have seen violence between protesters and riot police

Carles Puigdemont has handed himself in to Belgian justice authorities after Spain issued a new warrant for his arrest

Hundreds of thousands of pro-independence supporters from across Spain's northeastern region of Catalonia are pouring into Barcelona

Mr Puigdemont and a number of his associates fled to Belgium in October 2017 after they were summoned to court over the secessionist push he led and the holding of an independence referendum that the Spanish government said was illegal.

Spain's Supreme Court said an investigating judge has told Belgian judicial authorities that Mr Puigdemont possesses no parliamentary immunity that might prevent his extradition to Spain.

A court statement said Belgian authorities asked for clarification on the matter early on Friday.

Mr Puigdemont is sought by Spain on possible charges of sedition and misuse of public funds. He has so far avoided extradition from Germany and Belgium.

Mr Puigdemont is sought by Spain on possible charges of sedition and misuse of public funds

Spain's central authorities said that 46 flights into and out of the region were cancelled today due to the strike

A car in Estelada (Catalan separatist flag) colours drives as Catalan demonstrators march during Catalonia's general strike in El Masnou, Spain

The separatist leader was elected as a European legislator in May, but the court said Judge Pablo Llarena told Belgium that Mr Puigdemont did not take office because he did not swear on the Spanish constitution - a prerequisite under Spain's electoral rules.

In Barcelona today, thousands are waving pro-independence flags on the fifth day of protests following the jailing of nine separatist leaders.

The strike comes after another night of violence which saw separatists burning barricades and clashing with riot police as 58 people were injured, including a 17-year-old who was hit by a police van.

Protesters in Barcelona set fire to cars and large wheelie bins, overturned metal barriers and threw firecrackers at police, who pushed back with batons and shields.

Hundreds of young separatists chanting 'independence' set fire to improvised roadblocks in the centre of the city late in the evening, tossing Molotov cocktails at police, who responded by firing foam and anti-riot rounds.

Protesters burn barricades on a night of violence in Catalonia which saw clashes between separatists and riot police

Protesters in Barcelona set fire to cars and large wheelie bins, overturned metal barriers and threw firecrackers at police

Emergency services said 58 people were injured, including a 17-year-old who was hit by a police van.

Another 38 people were injured in protests in other Catalan cities, including Lerida and Girona.

Police have arrested 97 people across Catalonia since the protests began, Interior Minister Fernando Grande-Marlaska said yesterday.

The fresh clashes came on the eve of a huge protest in the Catalan capital today with hundreds of thousands taking to the streets.

Spain's central authorities said that 46 flights into and out of the region were cancelled today due to the strike called by pro-independence unions.

Picketers have also blocked the border with France at the major crossing point of La Jonquera.

Separatists have called the general strike and rally today 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.

'The actions we have been staging over the past few days testify to the helplessness we feel as the Spanish state continues to reject (independence) and threaten us, while Europe remains silent,' a 23-year-old accountant, who would only give his first name as David, told AFP.

Eduard Salinero, a 21-year-old physics student who is in favour of secession, said many people who want Catalonia to remain a part of Spain back the protests 'because they feel it is totally unfair to send our elected politicians to jail'.

Catalan demonstrators block Diagonal Avenue during Catalonia's general strike in Barcelona today

Riot police responded with firing foam and anti-riot rounds, pushing back the protesters with batons and shields

Emergency services said 58 people were injured, including a 17-year-old who was hit by a police van

Police have arrested 97 people across Catalonia since the protests began this week

Hundreds of young separatists chanting 'independence' set fire to improvised roadblocks in the centre of the city late in the evening, tossing Molotov cocktails at police

Protesters burn a trash bin as they take to the streets to demonstrate after the Spanish Supreme Court sentenced nine Catalan separatist leaders

Activists blocked several roads across Catalonia by burning tyres while the commuter rail service in Barcelona was intermittently disrupted due to demonstrators on the tracks, officials said.

Several roads and highways were also blocked off due to the mass marches which departed on Wednesday from five Catalan towns heading for Barcelona.

Xenia Cabeza, 18, said she was protesting 'because they don't let us vote in a referendum' on secession. She carried a sign that read 'You can't imprison an entire people'.

Announced on Monday morning, the verdict has sparked three days of large demonstrations which have turned increasingly violent with separatist activists engaged in nighttime clashes with riot police in Barcelona and elsewhere.

While Catalan president Quim Torra has sanctioned and even encouraged civil disobedience, his government is also responsible for the regional police who are charged with controlling demonstrations, putting him in an uncomfortable position.

Torra had not commented on the unrest for days, but overnight he called for an immediate halt to the violent clashes, saying there was 'no reason or justification for burning cars'.

Another 38 people were injured in protests last night in other Catalan cities, including Lerida and Girona

The fresh clashes came on the eve of a huge protest in the Catalan capital today with tens of thousands taking to the streets

But just hours later, he pledged in Catalonia's regional parliament to push for a new vote on secession by the end of his term in early 2022.

'We must push forward and not allow ourselves to be intimidated by threats and bans,' he said.

A poll published in July by a public Catalan institute showed support for an independent Catalonia at its lowest level in two years, with 48.3 per cent of people against and 44 per cent in favour.

The court's decision has thrust the Catalan dispute to the heart of the political debate ahead of Spain's November 10 general election, its fourth in as many years.

According to the first poll since Monday's verdict, the ruling Socialists are likely to secure the most votes but again fall short of a majority.

The main opposition conservative Popular Party, which takes a hard line on Catalan separatists, looks set to make significant gains, it found.

Published in El Mundo daily, it predicted the Socialists will capture 122 seats in the 350-seat parliament, compared with the 123 it took in the last election in April, while the PP would win 98 seats, up from 66.