Violence has broken out at the end of an anti-austerity protest attended by tens of thousands of people in the Spanish capital Madrid.
Dozens of youths threw projectiles at police, who responded by charging at them.
Demonstrators were protesting over issues including unemployment, poverty and official corruption.
They want the government not to pay its international debts and do more to improve health and education.
The BBC's Guy Hedgecoe in Madrid says protesters travelled from all corners of Spain, many of them making the journey on foot, in order to voice their anger.
They called their protest the march of dignity, our correspondent says, because they say that the government of Mariano Rajoy is stripping Spaniards of just that.
For many of them, the cutbacks that Mr Rajoy has implemented, in particular to health and education, are causing Spain irreparable damage.
Although most of the demonstration took place peacefully, violence broke out later on Friday with a number of arrests and several policeman injured.
Analysts say that Spain came out of recession in the second half of 2013.
But unemployment soared with the government's labour reforms which reduced the cost of hiring and firing.