Strikes and demonstrations caused chaos across Europe yesterday as rioters clashed with police and cities were brought to a standstill.

Tens of thousands of people marched through Brussels in a protest against spending cuts in the European Union.

In Barcelona, a general strike turned violent, with officers firing rubber bullets after being attacked by a mob who set police cars on fire.

In flames: A police car burns during riots in Barcelona as Spanish workers stage a general strike to protest austerity measures

Target: Anti-capitalist protesters vandalize a police car during riots in Barcelona

Thousands of Britons were caught up in the chaos as the Spanish strikers grounded hundreds of flights.

Among those affected were Manchester United fans travelling to Valencia for their team’s Champions League clash last night.

Bleeding: A demonstrator reacts angrily after being hit by riot police during protests in Barcelona

Other left-wing demonstrations against austerity measures were held in Italy, Greece, Portugal, Ireland and Latvia.

Fears that widespread industrial action could spread to Britain are growing, with the Government intent on slashing spending by up to 25 per cent in some areas.

New Labour leader Ed Miliband insisted in his speech to the party conference this week that he would not back ‘irresponsible’ strikes. However, he has previously voiced support for the right to strike.

Yesterday’s Brussels march was organised by the European Trade Union Confederation, whose general secretary is John Monks, former leader of the TUC in Britain.

An estimated 100,000 demonstrators in bright red, green and blue union jackets marched through Brussels toward European Union buildings, aiming to reinforce the impact of Spain’s first nationwide strike in eight years. Shops and banks were barricaded and about 150 people were detained, some in scuffles with police.

In Athens, the metro system was shut down by a rail workers’ walk-out and doctors at state hospitals went on a 24-hour strike.

In Dublin, a 41-year-old man was arrested after blocking the gates of the Irish parliament with a cement truck to protest against the massive bailout of the Anglo Irish Bank.

A protester shows a victory sign during a Solidarity trade union demonstration against budget cuts, in front of the Polish government office, in Warsaw

Mobilised: Picketers march through central Valencia during today's nationwide general strike in Spain

Civil unrest: Police officers coral picketers in Valencia on a strike called by Spanish labour groups, including the two largest unions CCOO and UGT

Greek tragedy: Strikers clash with riot police during a rally in Athens in April - more protests are expected today

Greece has already been suffering from two weeks of protests by truck drivers who have made it difficult for businesses to get supplies.

Many supermarkets are seeing shortages, while producers complaining they are unable to export their goods.

Greece's government has imposed stringent austerity measures, including cutting civil servants' salaries, trimming pensions and hiking consumer and income taxes.

Attack: The cement mixer didn't make it past the gates of the parliament building in Dublin

Written across the truck's barrel in red letters were the words: 'Toxic Bank' Anglo and 'All politicians should be sacked'

In Dublin, a man blocked the gates of the Irish parliament with a cement truck to protest the country's expensive bank bailout.

Written across the truck's barrel in red letters were the words: 'Toxic Bank' Anglo and 'All politicians should be sacked.'

The union anger was fuelled by the EU’s proposal to penalise member states that have run up deficits.

Union leaders have pledged tough action against the austerity measures, claiming EU workers are becoming the biggest victims of the financial meltdown set off by bankers and traders.

Demonstrators hold banners as they march down a main boulevard in Brussels

A Spanish Civil Guard officer in full riot gear stands in front of a burning barricade blocking the A-8 highway in the northern Spanish village of Muros del Nalon

A passenger sleeps on a luggage trolley at the airport after many scheduled flights were cancelled as some air traffic controllers and ground crews honored the general strike call

The British Government is on a collision course with Brussels over the radical plans, with the Treasury saying the EU does not have the power to impose fines.

Mr Monks said: ‘There is a great danger that the workers are going to be paying the price for the reckless speculation that took place in financial markets.’

At least 40 people were arrested in Spain, where protesters set fire to a police car in Barcelona and tourists watched in horror as demonstrators clashed with riot police.

Ryanair axed 69 flights between the UK and Spain, while easyJet cancelled around half its flights.

Protests Against Austerity Sweep Europe