Spanish workers slowed public transport to a crawl and disrupted factories on Thursday in a protest over Prime Minister Mariano Rajoy's sweeping reforms a day before a new round of budget cuts.
Police barricaded parliament and other public buildings, and arrested 58 people, many of whom were trying to stop workers crossing picket lines to get to their jobs.
A handful of scuffles broke out, flights were grounded and groups of union members waving red flags gathered in Madrid.
Spaniards have been tolerant of Rajoy's efforts to reform the labour market and meet strict Europe-imposed deficit goals to make sure it does not face a Greek-style debt crisis and in many neighbourhoods it was business as usual.
But the strike, the first since September 2010, shows that patience with the three-month-old government may be running out.
This is the largest cut of (workers') rights since anyone can remember. There has to be a better way to get out of this crisis, UGT union member Marta Lois, 40, said on Madrid's main street Gran Via.
Unions said there was 85 percent turnout for the general strike while the centre-right government said the work day was proceeding normally.
Workers at auto factories Volkswagen and Renault followed the strike during the nightshift, union Comisiones Obreras said. Data from national grid operator REE showed demand for power was about 20 percent below expected at 07.40 a.m. British time.
Transport employees provided a previously agreed basic level of service, meaning one in four buses and about a third of underground and local trains were expected to run but only 10 percent of domestic flights and 20 percent of European flights.
Police presence was particularly heavy around parliament where lawmakers were due to debate measures to help heavily indebted local and regional governments pay money owed to suppliers.
Spain is now tipping into its second recession since the end of 2009 and some observers expect at least another million people to join already swollen unemployment lines.
The jobless rate is the highest in the European Union at 23 percent and almost half of under 25-year-olds are out of work.
Polls had predicted only 30 percent of workers would join Thursday's one-day strike against labour reform, but a surprise electoral setback for the ruling People's Party (PP), at two regional elections on Sunday may spur wider participation.
Sunday's election results are a sign that the population won't accept these kinds of reforms ... and could mark the start of a new cycle with more active opposition to policies than we've seen in recent months and year, economics professor at Spain's Santiago de Compostela University Xavier Vence said.
Spain's last general strike in September 2010, had limited impact beyond disruptions in transport and on factory production-lines as Spaniards resigned themselves to the then-Socialist government's austerity drive.
Left-leaning political website eldiario.es said this week the strike might help Rajoy in his dealings with European leaders anxious to contain the continent's debt crisis.
If we Spaniards accept this abuse with resignation, apathy and docility, the government won't have the will or the arguments to stand up to Brussels and Berlin, eldiario.es said.
Spanish unions called Thursday's strike to protest a jobs reform that makes it cheaper for companies to fire people and dismantles the nationwide system of collective bargaining.
The labour reform has taken away workers' rights my parents managed to win. This strike is just a starting point for protests and I see things ramping up in the coming months, said train driver Miguel Pastor, 40, at Madrid's Atocha station.
But union power has been slowly disintegrating, with fewer than a fifth of Spanish employees currently affiliated with the country's two biggest unions, Comisiones Obreras and UGT.
Under the circumstances the unions have to do something, but they don't really think it will do any good, said Jose Ramon Pin, professor at business school IESE.
Economy Minister Luis de Guindos dismissed unions' calls to change it. Regardless of whether (the strike) is considered a success or failure, the government is not going to alter the reform one jot, he said on Wednesday.
The fear of job losses may be a major deterrent for many workers to take part in the strike.
I've been waiting half an hour for the bus, but I have to go to work. I have a little girl and cannot stay away. The strike won't do anything to solve the crisis, said 35-year-old office worker Alma Callet.
Former PP Prime Minister Jose Maria Aznar backed down on his labour reform plans in 2002 after a general strike shut down a large part of the country.
And following Sunday's regional election result, which denied Rajoy the absolute majority he had hoped would reinforce his mandate for spending cuts, the prime minister will have to measure his next steps to avoid sparking more protests.
He said on Tuesday his administration would pass a very, very, austere budget on Friday and this year's deficit reduction goal of 5.3 percent of gross domestic product implies nominal cuts of at least 35 billion euros (29.36 billion pounds).
The strict budget is meant to keep borrowing costs down as well as working towards meeting the EU's 3 percent deficit limit next year, but some economists say spending cuts will deepen the looming recession.
(Additional reporting by Feliciano Tisera and Martin Roberts; writing by Tracy Rucinski; editing by Paul Day and Anna Willard)