More soldiers have been sent to Spain's flood-hit east on Monday where rescuers have scoured underground carparks for bodies and protests bubbled over the government's handling of a disaster that has killed at least 217 people.

The army sent about 5,000 soldiers over the weekend to help distribute food and water, clean up streets and guard against looters. 

A further 2,500 would join them, Defence Minister Margarita Robles told state-owned radio RNE.

A warship carrying 104 marine infantry soldiers as well as trucks with food and water was approaching Valencia port even as a strong hailstorm pummelled Barcelona some 300 kilometres to the north. 

An alert from regional authorities warned of potential landslides and more flooding.

Airport operator AENA said about 50 flights due to take off from Barcelona's partially flooded El Prat airport were cancelled or severely delayed, while 17 due to land there were diverted. 

Some local train services were also cancelled.

Fatalities from Spain's worst flash floods in modern history edged higher to 217 on Sunday, almost all of them in the Valencia region and more than 60 in the suburb of Paiporta.

Rescue teams searched car parks and river mouths where currents may have deposited more bodies.

Locals criticised late alerts from authorities about the dangers and a perceived delayed response by emergency services.

On Sunday, some residents in Paiporta slung mud at Prime Minister Pedro Sanchez and King Felipe and his wife Queen Letizia, chanting: "murderers, murderers!"

Photos showed Mr Sanchez's official car with broken windows.

Some people protesting on Sunday against Sanchez in the Valencia region wore clothing with the symbols of far-right organisations. 

Ms Robles said extremist groups were taking advantage of the situation for political gains.

Unions and left-wing cultural associations have announced a protest in Valencia on Saturday to call for regional president Carlos Mazon, of the conservative People's Party, to step down.

A daily protest in Madrid outside the headquarters of Mr Sanchez's Socialist party drew more people on Sunday — approximately 600 — due to anger over the floods, according to El Pais newspaper.

Opposition politicians accused the left-wing central government of acting too slowly to warn residents and send in rescuers, while Madrid has said regional authorities were responsible for civil protection.

Lack of clarity over numbers of dead and missing has added to frustration. 

A landline has been set up for relatives to report the missing, with the government saying "dozens and dozens" are still unaccounted-for.

Coroner services on Sunday said 183 autopsies had been performed, and 67 people were identified.

The government said on Sunday the death toll had stabilised because all victims on the surface had been identified.

The midweek torrential rains caused rivers to swell, engulfing streets and ground floors of buildings, and sweeping away cars and masonry in tides of mud.

It was the worst flood-related disaster in Europe in five decades. 

Scientists say extreme weather events are becoming more frequent due to climate change.

Meteorologists think the warming of the Mediterranean, which increases water evaporation, plays a key role in making torrential rains more severe.

Even though rainfalls have continued during the rest of the week, there has been no more major flooding in the area.

Reuters