About 50 planned marches were expected to take place in cities including Madrid, Valencia and Barcelona, with some already under way. In Valencia, one of the first protests started, with photographs showing a large crowd marching through the streets.
"There is a lot of anger in the streets," said a spokesperson for the Valencia Tenants' Union. Clashes have taken place between some protesters and police in the city.
The measures put forward by Prime Minister Pedro Sánchez's leftist coalition government on Friday followed public outcry over the eviction of an 87-year-old woman from her home last month after she was unable to afford a sharp rent increase. Her eviction triggered nationwide protests, with demonstrators demanding lower rents, an end to evictions, and a ban on investment funds buying property.
Sánchez's defeat in Congress on Friday heightens speculation that he might call an early general election, which was not due until next summer. His coalition government, made up of his ruling Socialist party and junior partner the Sumar alliance, does not command a majority in parliament.