Masses of chanting "indignant" activists poured into the streets across Spain on Saturday in a vast show of strength one year on from igniting a global protest against economic injustice. Tens of thousands packed Madrid's central Puerta del Sol square, the emblematic birthplace of their popular movement against inequality, sky-high unemployment and spending cuts that shook the political establishment. Many had marched to the square for hours in separate columns of protesters from all directions and defied an official warning that they must disperse after 10:00 pm (2000 GMT). At midnight, as promised, they lifted their arms to the sky and held a minute of silence before chanting; "Yes we can, yes we can," in a gesture of defiance. In the early hours of Sunday, several thousand protesters remained in the square, surrounded by numerous police cars parked in nearby streets. Madrid police estimated that 30,000 people had taken part in the protest during the day. In Barcelona, Spain's second city, the turnout was 45,000 according to police, and 220,000 according to organisers. The marches, held in 80 cities and towns across Spain, launched a four-day protest that will end on May 15, the anniversary of the movement's birth -- dubbed 15-M. The movement, which relies heavily on online social networks to campaign and organise, has inspired similar protests from Britain to the Occupy Wall Street campaign in the United States. "We never ceased to exist. It is not that we have returned, we never left," said a 25-year-old nursing intern in Barcelona, adding that she planned to camp overnight in the square. While Barcelona city hall seemed prepared to tolerate a camp for a limited period, the authorities in Madrid insisted that they will not allow a repeat of last year's month-long sprawling encampment in Puerta del Sol that included everything from a canteen to a kindergarten and a library. Spain's conservative government, in power since December, has issued a permit for the "indignants" to use Puerta del Sol for a five-hour assembly Saturday and for 10 hours on each of the following three days. Deputy Prime Minister Soraya Saenz de Santamaria said the government would ensure that the regulated hours are respected. A year after the movement's birth, Spaniards have even more to protest: a recession, unemployment at 24.4 percent for the general workforce and 52 percent for the under-25 population, and more than 30 billion euros ($39 billion) worth of austerity cuts so far this year. "We are here because we continue to be angry over the austerity policies which an economic elite is imposing on us," said 21-year-old philosophy student Victor Valdes at the Madrid rally. Another protester, 23-year-old office worker Marina Santos said: "It is important to show that we are still here, that there are thousands of people that want a change and are willing to work for it." She carried a handmade sign that read: "Another World is Possible" as she marched to Puerta del Sol to the beat of drums. The "indignants" have staged overwhelmingly peaceful protests and neighbourhood assemblies since their camp at Puerta del Sol was dismantled on June 12, but interest has tapered off. "The movement has mutated, it is still there. What has happened is that it is not on the streets, it is online and in social networks," said Noelia Moreno, a former spokeswoman for the movement in Madrid. "This is a long-distance race, no one can change an entire political system in one day or one year, it takes time," the 30-year-old unemployed video producer added. Critics charge that beyond staging rallies, the movement has had little impact. Antonio Alaminos, sociology professor at Alicante University, said the "indignants" had failed to organise and were left expressing a discontent born from social and economic malaise without a concrete ideology. "The result: lots of small relatively disconnected groups that no longer form a social movement," he said.