"No more violence, discrimination or pay gap!"
In a seated protest, they blocked two lanes of a central thoroughfare as police directed traffic around them.
"We need to change the laws, but also the culture, the society we have created", said Roberto Guerra, a union representative at the National University of Distance Education. Ada Colau, the mayor of Barcelona, said she would join the strike.
The theme of Thursday's International Women's Day 2018 is #PressForProgress, but that's not the only message that activist women have sent.
German Chancellor Angela Merkel, one of the world's most powerful women, said in a video message that the quest for greater gender equality in Germany and worldwide must continue.
"We're giving visibility to work that no one wants to recognise, whether it's at home or badly paid or done in the invisible economy", said the organisers.
Across Asia, women came out to mark the day.
In a speech marking International Women's Day, she said, "A country's human rights values will be enhanced when women are granted their rights".
In the Philippine capital of Manila, hundreds of women dressed in pink and purple took to the streets to protest the 4,000 people killed under President Rodrigo Duterte and his heavy-handed crackdown on illicit drugs.
Nonetheless, several US companies, including McDonald's, Kroger and Old Navy, made gestures in recognition of the day, and the White House announced that first lady Melania Trump would present State Department courage awards to women from around the world at a March 21 ceremony.
International Women's Day is celebrated on March 8 every year. South Korea's anti-sexual violence movement has gained significant traction since January, when a female prosecutor began publicly raising workplace mistreatment and sexual misconduct. The movement has spread across the Asian economic giant after a female prosecutor revealed in January that she had been assaulted by a colleague several years ago, leading to the downfall of numerous high-profile men, including a provincial governor who was a leading presidential contender before he was accused of raping his secretary.
In India, hundreds of women, including students, teachers, and sex workers, marched through the capital to bring attention to domestic violence, sexual attacks, and discrimination in jobs and wages.
At present, some 48.5 per cent of women and girls over the age of 15 are part of the global workforce, the International Labour Organisation said in a report.