Spain's coronavirus death toll soared past 19,000 on Thursday with another 551 deaths, but questions over the counting method have raised some regional concerns the real figure is much higher.

After nearly five weeks of confinement, the rise in deaths and infections has slowed over the past fortnight, with the overnight fatalities taking the toll to 19,130.

But regional authorities in Madrid and Catalonia said they each had thousands more victims than the official count. "The real number of deaths is difficult to know," said Fernando Simon, the health ministry's emergencies coordinator.

The daily figure was compiled from information provided by regional authorities concerning deaths among patients who "had tested positive for coronavirus", he said.

Between them, Madrid and Catalonia account for 56 percent of the national toll, but some officials say the numbers are flawed for not including those who have died at an old people's home or in their own home. Madrid has counted 6,877 deaths but on Wednesday a top official said the true figure was likely to be more than 10,000.

In Catalonia, where 3,855 people have died, the real number could be higher than 7,000 -- prompting the regional government to announce changes to its counting method.

Deaths outside of hospital

"Until now, the official figures were supplied by Catalan hospitals counting people who died there," it said in a statement late on Wednesday.

"But as of today.. figures on deaths at (old people's) residences and homes throughout Catalonia will also be collected following an order to funeral services to provide this information," it said, giving a new figure of 7,097.

It did not say by what criteria the funeral services were determining the cause of death -- in an issue picked up on by Simon, who said it was important to verify whether or not those victims "had tested positive or not".

Among the latest wave of victims was best-selling Chilean writer Luis Sepulveda, who died at a hospital in the northern city of Oviedo, his publishing house said. Spain also recorded 5,183 new cases of COVID-19, taking the overall figure to 182,816 -- officially second highest in the world behind the United States.

Spanish officials say the virus has steadied since a daily toll of 950 was recorded on April 2 but they have insisted on maintaining the March 14 lockdown that is likely to be extended into mid-May.

One of the tightest lockdowns in Europe, the restrictions allow just essential workers out, otherwise, the rest of the population can only leave home to buy food and medicine, to attend a medical emergency or to briefly walk the dog.