The devastating Mediterranean storm that lashed eastern Spain a week ago triggered surging torrents of muddy water that have left a trail of destruction and an unknown number of missing.

Around 17,000 security force and emergency services personnel are working around the clock to repair damaged infrastructure, distribute aid and search for bodies in Spain's largest peacetime deployment of its armed forces.

Firefighters painstakingly combed through piles of damaged vehicles and pumped out water from inundated garages and car parks where more victims may be discovered, AFP journalists saw.

Maribel Albalat, mayor of the ground-zero town of Paiporta, told public broadcaster TVE they were doing "better, but not well" with many streets still inaccessible and residents struggling to get a phone signal.

Prime Minister Pedro Sanchez chaired a cabinet meeting on Tuesday where Spanish media reported he would declare the stricken regions "gravely affected" to facilitate more aid.

Castilla-La Mancha, Andalusia, Catalonia and Aragon could be included along with the ravaged eastern Valencia region which has suffered almost all the deaths and damage, they said.

Five working groups between the left-wing national government and the conservative-run regional authority have been created to coordinate the recovery in Valencia and overcome their occasionally tetchy relationship.

- 'Only the people are helping' -

But many survivors are furious with the authorities for failing to warn the population on time last Tuesday and provide urgent rescue and relief work.

That anger reached breaking point in Paiporta on Sunday when crowds heckled and hurled mud at King Felipe VI, Queen Letizia and Sanchez.

"Only the people are helping... And the politicians, where are they? Why didn't they raise the alarm? Murderers!" Matilde Gregori, 57, told AFP in the mud-soaked town of Sedavi.

"They don't know how to take care of their people, let them go home... We know how to do better," said Gregori, whose shop fell victim to the floods.

The authorities have warned survivors to shield themselves from health hazards in the stagnant flood water, which may contain toxic waste, chemicals or bacteria from dead humans and animals.

Biology teacher Jose, 58, wore a mask and gloves during the clean-up of a garage in Sedavi awash with water for almost a week.

"Having stagnant water that can breed germs is a great danger that we want to avoid... we'll see if we can manage," he told AFP.

Storms coming off the Mediterranean are common during this season. But scientists have warned human-induced climate change is increasing the ferocity, length and frequency of extreme weather events.