Organised demonstrations have recently taken place in capital Madrid, as well as in Malaga and Valencia, as inflation continues to rise.
The FCDO updated its advice for Spain late last week to reflect the situation.
"Demonstrations, political gatherings, or marches may take place in Spain with little or no warning, particularly in cities," said the FCDO. "You should follow the advice of police and local authorities.
"While the vast majority of demonstrations are peaceful, there is a risk of isolated incidents of unrest or violence.
"If you’re in and around areas where demonstrations are taking place, remain vigilant and move away quickly if there are signs of disorder."
