Carlos Mazon has faced fierce scrutiny over his handling of the October 29, 2024 catastrophe that killed more than 230 people, consistently rebuffing calls for his resignation.

His regional administration -- primarily responsible for the emergency response under Spain's decentralised system -- sent alerts to residents' mobile phones when flooding had already started in some places.

The alert also came more than 12 hours after the national weather agency had issued its highest alert level for torrential rains.

Relatives of the victims shouted "murderer", "coward" and "get out" at Mazon as he arrived for the ceremony in the Mediterranean city of Valencia.

As the event ended, they again hurled insults at him, with the cries including "resign", "son of a bitch" and "you should be in prison".

Others had tried to shout them down, asking for respect.

- Learning 'lessons' -

King Felipe VI, Queen Letizia and Prime Minister Pedro Sanchez led political leaders, senior officials and mourners at Valencia's City of Arts and Sciences, a cultural and architectural complex.

Felipe, who rarely makes political interventions, indirectly referred to the controversy in a speech that emphasised the need to "continue analysing the causes and circumstances of the tragedy".

Such action aimed "to rigorously and calmly draw the necessary lessons to improve our ability to face other major catastrophes in the future, and avoid or minimise their worst consequences as much as possible," he said.

Around 800 relatives of the victims were present, a handful of them wearing shirts showing photographs of their deceased loved ones. One bore the words "They were avoidable deaths", and another "Justice".

The proceedings included the reading out of each victim's name, a dirge, speeches by relatives of the victims and a minute's silence.

"For us, the most important thing is that truth, respect and humanity prevail," said Andrea Ferrari Canut, a daughter of one of the dead.

In last year's disaster, torrential rain unleashed flooding that killed 229 people in towns near Valencia.

Seven more people died in the neighbouring Castilla-La Mancha region, and one person died in Andalusia in the south.

The deluge swept away 130,000 vehicles and damaged thousands of homes, generating 800,000 tonnes of debris.

- Wounds 'never fully heal' -

Despite signs of severe flooding, Mazon went ahead with a long lunch with a journalist on the day of the catastrophe.

He has defended his handling of the crisis, saying its magnitude was unforeseeable and that central authorities did not provide sufficient warning about the severity of the rain.

"We did our best under unimaginable circumstances, yet in many cases it was not enough, and today we must once again acknowledge that reality," Mazon said in a televised address ahead of the memorial.

More than 50,000 people took to the streets of Valencia city on Saturday to demand that Mazon resign, the latest in a string of such demonstrations.

The regional government declared a day of mourning, while the town of Paiporta, at the epicentre of the disaster, will observe three days of remembrance.

On one of Paiporta's main streets, a pharmacy placed a row of red and white candles on the ground by its entrance to honour the deceased, an AFP journalist saw.

"I think Paiporta will take many years to be like it was, in terms of streets and houses, and I don't think the wound will ever fully heal," said Carmen Rausell, a 61-year-old pharmacist, her eyes welling with tears.