MADRID, Spain — Millions of Spanish workers walked off the job Wednesday in a nationwide strike over soaring rents, a shortage of affordable homes and rising evictions. Demonstrations drew crowds in Madrid, Barcelona and cities across the country, with unions estimating that 4 million people took part — roughly one-fifth of Spain’s workforce.

The walkout, the country’s first general strike since 2012, disrupted ports, industrial plants and public services. Demonstrations were largely peaceful during the day, unions said, but clashes between police and protesters broke out in parts of Madrid and Barcelona by evening.