The interior ministry said 32 people had been arrested and 15 people treated for minor injuries following disturbances in Spain, as strikes and protests against austerity measures took place across Europe.
The General Workers Union said the stoppage, the second in Spain this year, was being heeded by nearly 100% of workers in the motor, energy, shipbuilding and construction industries.
But ministry official Cristina Diaz played down participation, saying it was hardly noticeable in goods haulage and major city wholesale food markets.
She said electricity consumption, a gauge of industrial activity, was down 11% on a normal working day.
With a 25% unemployment rate, Spain is at the core of Europe's debt crisis.