The leader of Spain's Valencia region defended his handling of catastrophic floods that killed more than 200 people, saying on Friday he did everything possible in the face of a "monstrous avalanche of water that exceeded all weather forecasts".

Protesters and police clashed in the streets of Valencia in eastern Spain on Saturday, as tens of thousands of people marched to demand the regional president resign over his response to floods that killed more than 220 people.

Carlos Mazon, leader of Spain's Valencia region, faces criticism over his response to catastrophic floods that killed 200 people. Despite calls to resign, Mazon defends his actions, acknowledging failures and promising a public inquiry.

The head of Spain's eastern Valencia region admitted Friday to "mistakes" in handling the country's deadliest flood in decades that killed 216 people there and apologised.