MADRID (AP) -- Flag-waving Spanish workers livid over labor market reforms they see as flagrantly pro-business blocked traffic Thursday, formed boisterous picket lines outside wholesale markets and bus garages and kept some TV programming off the air.
Unions said car factories and other industrial sites saw very strong support for the stoppage protesting what they see as the latest taste of bitter medicine the new conservative government of Prime Minister Mariano Rajoy has prescribed to appease European Union overseers and international investors watching the size of Spain's debt burden and the poor health of its GDP.
The government downplayed the strike as not having a major impact, however.
There were no reports of significant violence.
A total of 58 people were detained and nine were injured in scuffles as the strike got under way a minute after midnight, Interior Ministry official Cristina Diaz said.
Unions are challenging a conservative government not yet 100 days old, protesting changes to labor market rules long regarded as among Europe's most rigid. Among other things the changes make it cheaper and easier for companies to lay people off and let them cut their wages unilaterally.
On the Gran Via, one of the Spanish capital's main commercial strips, a group of about 500 whistle-blowing picketers marched slowly up the avenue, blocking traffic for about an hour. Police in black uniforms watched them from the sidewalk and followed from behind to keep them going, like shepherds. Helmeted riot police sat in vans nearby.
At one point the strikers stopped outside a McDonald's restaurant and yelled at people inside for crossing a picket line. As the group made its way down the boulevard, many merchants -- such as jewelers and clothing retailers -- pulled down their metal shutters until the crowd passed by, or locked their front doors to keep strikers out.
One protester, Angel Andrino, 31, said he was laid off a day after the labor reforms were approved in a decree last month. The government says that it understands the reforms might hurt now but it argues it will create jobs down the road when the economy recovers. Spain is already in recession, according to the central bank.
Andrino marched with his parents and brother. They all live together. The brother is the only one with work and it is only part-time.
"We are going through a really hard time, suffering," he said. "The rights that our parents and grandparents fought for are being wiped away without the public being consulted."
Outside a major department store, 69-year-old retiree Jose Antonio Nunez was dressed up in a skeleton's costume and carried a toy scythe. On the side of the blade was the word "wages." Nunez said he is struggling to get by on his retirement pension and fears more pain for everyone when an austerity budget is unveiled Friday.
"I am dressed like this because with the wages they are paying they are going to wear us down to the bone," Nunez said.
Outside the headquarters of the ruling Popular Party, strikers slapped hard-to-remove pro-strike stickers on the windows of restaurants and shops that remained open, and spared those that were closed. Cleaning attendants scraped away arduously to try to get the stickers off.
Unions are challenging a conservative government not yet 100 days old, protesting changes to labor market rules long regarded as among Europe's most rigid.
The demonstrations come just a day before the government will serve up even more austerity pain with a 2012 budget to feature tens of billions of euros (dollars) in deficit-reduction measures.
Around Spain, unions tried to bring the country to a crawl by guaranteeing only around 30 percent of normal public transport service at rush hour times.
The main airline, Iberia, canceled 65 percent of its flights.
National airport operator AENA said that by midmorning 402 flights had been canceled. It said minimum services decreed by law ensured that 1,675 flights would operate -- less than half of the average daily amount of more than 4,500 flights.
British Airways said its flights were operating normally but advised passengers to check the status of their flights before heading to the airport.
TAP Air Portugal said it canceled just over half of its 27 scheduled return flights to Spain.
The union UGT said virtually all workers at Renault, SEAT, Volkswagen and Ford car factories around Spain, and at other industrial, mining and port facilities, honored the strike during the overnight shift. UGT said that overall participation in the strike so far was "massive."
Picketers tried to block wholesale markets in Madrid and other cities and commuter train service were disrupted in Barcelona, but otherwise the situation was fairly normal in the early hours of the strike, Cristina Diaz, a spokeswoman for the interior ministry said.
Outside Atocha, one of Madrid's main commuter and long-distance rail stations, picketers waved red union flags and blew shrill whistles as police looked on. Some picketers tried to convince a coffee shop owner to join them, and slapped a pro-strike sticker on his glass window.
Diaz said a Molotov cocktail was thrown at a police car in the eastern city of Murcia. Of six people injured, one was a police officer and five were civilians. She did not specify where or how these people were hurt.
Spanish National TV showed footage of police in Madrid on horseback accompanying buses trying to leave a parking garage, and scuffling with a picketer. Regional TV stations in Andalusia in the south, Catalonia in the northeast and Madrid were off the air because of the strike.
The government's cuts are designed to help Spain in its struggles to satisfy both the European Union and the international investors who determine the country's borrowing costs in the international debt markets-- and therefore have a lot of say in whether Spain will follow Greece, Ireland and Portugal in needing a bailout.
The government says it will not falter in its austerity drive, calling the reforms essential to creating jobs and reviving an economy that is expected to contract 1.7 percent this year.
"The question here is not whether the strike is honored by many or few, but rather whether we get out of the crisis," Finance Minister Cristobal Montoro said. "That is what is at stake, and the government is not going to yield."
Barry Hatton contributed from Portugal.