MADRID (AP) -- Flag-waving Spanish workers livid over labor reforms they see as flagrantly pro-business blocked traffic Thursday, forming boisterous picket lines outside wholesale markets and bus garages, as part of a nationwide strike.
Unions claimed massive participation in the 24-hour stoppage protesting what they claim to be the latest dose of bitter medicine Prime Minister Mariano Rajoy's conservative government has prescribed to appease European Union overseers and jittery investors watching Spain's debt grow and its GDP shrink.
The unions demanded a "gesture" from the government to scale back the reforms, warning they could cause more unrest from May 1.
The government quickly said no, and downplayed the impact of the strike, which failed to bring the country to a standstill. "There is no stopping on the path to reform," Labor Minister Fatima Banez said.
In fact, the government will on Friday serve up even more austerity pain with a 2012 budget to feature tens of billions of euros (dollars) in deficit-reduction measures.
The cuts are designed to help Spain lower its deficit to within EU limits and calm the international investors who determine the country's borrowing costs in debt markets -- and therefore have a lot of say in whether Spain will follow Greece, Ireland and Portugal in needing a bailout.
There were no reports of significant violence in Thursday's demonstration. 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, blocking traffic for about an hour. Police and helmeted riot police watched from the sidelines.
As the group made its way down the boulevard, many merchants -- such as jewelers and clothing retailers -- pulled down their metal shutters or locked their front doors.
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 argues that while the reforms might hurt now, they will create jobs in the future. Spain is by official estimates already back in recession.
Andrino lives with his parents and brother, the latter the only one to be employed, with a part-time job.
"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."
General Workers Union Secretary General Candido Mendez put average participation at midday at 77 percent but said that it was 97 percent in industry and construction. "This strike has been an unquestionable success," said Mendez.
Some statistics, however, suggested the strike had not brought the country to a standstill.
Electricity consumption -- a measure of industrial and commercial activity -- was down by 17 percent at midmorning, according to the Interior Ministry. That is slightly less than during the last general strike in 2010, which was deemed as only partially successful.
Investors are worried about prospects for continued, widespread social unrest of the kind seen in bailed-out Greece. But management professor Jose Ramon Pin of IESE Business School said this will not happen in Spain because people reluctantly accept that the country needs a radical economic makeover.
"This country is in no mood for taking to the streets," Pin said.
One of the strike's most noticeable effects was on public transportation, with unions guaranteeing only around 30 percent of normal service at rush hour times. The main airline, Iberia, canceled 65 percent of its flights.
By midmorning, 402 flights had been canceled, National airport operator AENA 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.
Diaz, the Interior Ministry official, 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.
Barry Hatton in Lisbon, Portugal contributed to this report.