Towards the end of the demonstration, angry protesters clashed with the police.
Pictures show Valencia’s city hall covered in mud, while Reuters reports that protesters are throwing chairs and other objects.
The city’s mayor, María José Catala, posted photos of broken windows and a video of the fire on social media, adding: “Vandalism is not the solution.”
Valencia’s city council condemned the “vandalism”, saying the city was also affected by the flooding.
Anna Oliver, one of the organizers of the protest, told the Reuters news agency: “We want to show our outrage and anger at the mismanagement of this disaster that has affected so many people.”
Last week, angry protesters pelted the King and Queen of Spain with mud and other objects during a visit to the town of Paiporta, one of the hardest hit.
Objects were also thrown at Prime Minister Pedro Sánchez, who was quickly evacuated.
Thousands of people have lost their homes, and streets in many areas are still covered in mud and debris.
Mazon, from the conservative People’s Party, defended his actions. He says his officials did not receive enough warning from the central government and the scale of the disaster was unpredictable.