Spain's death toll from the coronavirus rose by 769 overnight to 4,858, but a senior health official said the daily increase in the number of fatalities was stabilising.

Spain is second only to Italy in the number of coronavirus deaths worldwide and the number of people infected in the country rose overnight to 64,059 from 56,188 on Thursday.

"Today we have more deaths than registered yesterday, but it is also true that in percentage terms, today's increase is roughly equivalent to that of the past three days, in which we seem to see a clear stabilisation," health emergency chief Fernando Simon told a news conference.

The rise in the death toll in the previous 24 hours in percentage terms was about 19%, according to a Reuters calculation.

Spain is struggling to cope with the outbreak, with a Real Madrid soccer stadium being used as a medical supply store and a fairground in Madrid turned into a mass testing area.

Patients continue to stream into Spanish hospitals, where staff face a shortage of protective gear such as masks.

More than 9,400 health workers have tested positive for the virus, Simon said. That is about 15% of those infected in Spain.

Spain extended a nationwide lockdown on Thursday by a further 15 days to April 12 and said it was fighting a "real war" over medical supplies to contain the death toll. It is turning to China, where the coronavirus originated, for many critical products.

Schools, bars, restaurants and shops selling non-essential items have been shut since March 14 and most of the population is house-bound as Spain tries to stop the virus spreading.