Paying their respects to those who have perished during the pandemic, the family stood in front of a Spanish flag at half-mast in the grounds of the royal estate.
In 1975, when dictator Gen. Francisco Franco died, a 30-day mandatory mourning period was declared.
Spanish Prime Minister Pedro Sanchez said on Twitter this would last for "10 days, the longest period of mourning in our democracy, in which we will all express our sorrow and pay homage to those who have died".
Starting Wednesday until June 5, flags will be at half-mast in more than 14,000 public buildings across the nation as well as on the navy's vessels, the government announced.
The mourning period was approved at Tuesday's cabinet meeting, and government spokeswoman Maria Jesus Montero said there would also be a ceremony to honour the victims presided over by King Felipe VI.
No new cases of Covid-19 reported
The Wood County Health Department and Wood County Coroner is releasing new information on the May 22 COVID death. Mecklenburg County has seen a total of 2,954 coronavirus cases, according to state health data Friday morning.
The total number of deaths, has now been rising by less than 100 a day for over a week, compared with a peak of 950 in early April.
On Monday the government revised down the country's overall death toll from the epidemic by almost 2,000, and while Tuesday's reported cumulative toll of 27,117 was 283 higher than Monday's, the ministry said just 35 people had died from the disease over the past seven days.
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"It is something that happens in every epidemic, when the evolution of the epidemic leaves us with a bit more time, you have to correct the figures and in certain cases you have to reduce them", he explained.
Criticism of the left-wing government's handling of the crisis has boiled over into street protests in parts of the politically polarized country.