The thousands of positive tests bring the Spanish total from 213,024 to 219,764 in the biggest increase since 7,026 were recorded on April 4.
The jump is partly explained by the growing use of antibody tests, which have added nearly 17,000 people to the total since they were introduced.
There was also better news for Spain today as the daily death toll fell to 367, the lowest since March 21, taking the total from 22,157 to 22,524.
This graph shows the daily number of new coronavirus cases in Spain, which leaped to 6,740 today – the highest figure since April 4
However, deaths fell to 367 in their smallest jump since March 21, as seen on this graph
Spain said today that 16,774 people had tested positive via the antibody test method, an increase of 3,944 from yesterday’s total of 12,830.
Only 2,976 of the 6,740 new cases were confirmed using a traditional PCR test, official figures showed.
The Madrid region accounted for 1,097 of those while the second worst-hit region of Catalonia was responsible for another 652.
Antibody tests show whether a patient’s immune system has developed defences against coronavirus, meaning they have been infected in the past.
However, governments in several countries have warned that antibody tests are not yet reliable enough to roll out on a large scale.
Spanish health officials believe the epidemic peaked on April 2 when 950 people died over 24 hours, nearly three weeks after the government imposed a lockdown.
‘We have achieved the goal of a deceleration and slowdown for this week but we remain in a hard phase of the epidemic,’ health minister Salvador said yesterday.
The March 14 lockdown has been twice extended and parliament late on Wednesday approved a fresh extension until May 9,
However, conditions will be slightly eased from Sunday to allow children to spend some time outside.
Healthcare workers attend to a coronavirus patient at the intensive care unit of the La Paz University Hospital in Madrid yesterday
Medical workers wearing protective suits perform a tracheotomy on a coronavirus patient at a hospital in Madrid yesterday, in the worst-affected region of Spain
Prime Minister Pedro Sanchez hopes to ease some restrictions in the second half of May but warns that ‘de-escalation will be slow’.
In Madrid, authorities began shutting down hotels that had been hastily converted into medical centres after the outbreak left city hospitals unable to cope.
Spain started easing restrictions for some businesses last week, but restaurants, hotels and public spaces remain shut.
Hotels saw a 66 per cent plunge in foreign visitors in March, even though a shutdown only came late in the month.
Tourism usually accounts for 12 per cent of gross domestic product in the world’s second-most visited nation.
In further evidence of a downturn, automotive industry association Anfac said March car production fell 45 per cent year-on-year as factories stood empty.
Meanwhile, a new study suggests that the virus may have been circulating among the population as early as mid-February, when the government only acknowledged ‘community transmission’ in early March.
The scientists at Madrid’s Instituto de Salud Carlos III also found that the virus entered Spain via at least 15 different points.