Spanish workers angry at a labour reform the government calls an "unstoppable" necessity staged a general strike on Thursday, bringing factories and ports to a standstill and igniting flashes of violence on the streets.
Tens of thousands of protesters packed a square in central Madrid to vent their anger at the labour reforms and deep spending cuts, while in Barcelona, police fired rubber bullets to disperse a crowd that had set bins ablaze on the sidelines of a demonstration.
Thursday's strike was called by trade unions protesting against labour reforms and spending cuts which the conservative government says are needed to save the economy, and has resulted in some mild clashes and detentions of at least 58 people so far.
"This is a just response to a brutal reform of our system of labour relations," Ignacio Fernandez Toxo, leader of the CCOO, one of the main trade unions, said.
The strike is the first major walkout against the government's policies, just three months after Mariano Rajoy, the prime minister, took office promising to cut Spain's 23 per cent unemployment rate and stabilise its public finances.
Al Jazeera's Barnaby Phillips reporting from Madrid said: "They have succeeded in bringing a lot of disruption around Spain today, there's no doubt about that. People have talked about trade union influence being on the wane in Spain ... but they've hit transport links very hard across the country, many businesses, many factories have been closed.
"We'll have to wait and see the final balance, if you like, of who went to work and who didn't but on the face of it, this does look like a substantial disruption to normal economic life in Spain today."
The new laws would make it easier for companies to fire workers, but the government argues that in the long run the liberalisation of labour laws will bring unemployment down.
Demonstrators, brandishing a sea of red flags of Spain's major UGT and CCOO unions, marched down the Spanish capital's main streets towards the central Puerta del Sol square.
Bus depot scuffles
Scuffles broke out between protesters and police as workers picketed the capital's bus depot early on Thursday.
Around 100 protesters gathered in front of Fuencarral's bus depot and some of them blocked the road as the first bus departed form the depot. Tensions rose as riot police wrestled some protesters to the ground.
The interior ministry said a total of 58 people were detained and nine were injured.
A recent poll showed that three quarters of Spaniards are against labour reform, but a majority also believe that a general strike may make the situation worse. Only 30 per cent of workers would join the walkout, according to polls.
One of the protesters in Madrid, 35-year-old automobile salesman Jose Luis Rodriguez, said he had chosen to lose a day's pay to defend his rights by striking for the first time in his life.
"This strike day is going to cost me 60 euros ($80). It is not much compared to what they might take from me tomorrow with the reform. They can throw me into the street," he said.
"They are attacking workers' rights. If we don't go into the streets they won't know we're against the reform."
Unions called for protests to be held in about 100 cities and towns on Thursday evening.
'Very austere budget'
Under an agreement between the government and the two main unions, at least a minimum service of a third of local trains and buses is due to run, with one in 10 domestic and one in five European flights.
Airlines Iberia, Air Nostrum and Vueling have cancelled about 200 flights each from Spanish airports.
A minimum service is also planned in hospitals while schools and nurseries are due to open.
The national strike comes a day before the government unveils its 2012 budget, raising the heat on Rajoy who also faces pressure from European leaders to cut Spain's public deficit and avert further financial instability in the eurozone.
Rajoy, who has promised a "very austere budget", has defended his measures, including labour reforms which make it easier for firms to hire and fire and reduced severance pay for laid-off workers.
He says the proposed legislation would eventually generate more jobs.
"No government has passed as many reforms in its first 100 days in office as this one," Rajoy said.
"That's probably why there is a general strike," but it "will not solve Spain's problems, the biggest mistake would be to do nothing," he added.
Rajoy has so far this year confirmed $11.85bn worth of spending cuts and $8.39bn in tax rises, but economists say total cuts worth more than $66.6bn are needed.
"It's undoubtedly been a testing few days for this centre-right government. They didn't do as well as they had hoped in regional elections earlier and now of course they've had these big demonstrations and strikes today," reported Al Jazeera's Phillips.
"But all the signs are tomorrow that they will push ahead with a budget which they say is very, very austere. And undoubtedly that will not be popular with precisely the kinds of people who are demonstrating on the streets today."