Fears were growing of a spiralling coronavirus death toll among the elderly in Spain on Monday after military units sent in to offer emergency healthcare assistance and disinfect old people's homes found an unspecified number of abandoned dead bodies.

According to Spain's Ministry of Defence, the military teams found most staff had stopped going to work in several privately-run centres after residents began to fall ill with Covid-19, leaving the sick and dying unattended.

Defence Minister Margarita Robles said: "The full force of the law will be brought against those who do not fulfil their obligations."

Spain was shocked last week when it was revealed that 25 elderly people had died of coronavirus at the Monte Hermoso home in Madrid, mostly without being transferred to hospital. Dozens more pensioners have perished in other privately-run centres that have been overwhelmed by the epidemic.

Spain's government used its emergency powers to place private residences under the control of regional authorities, and on Monday the CCOO union in Madrid warned of a "bloodbath" if urgent action was not taken in such establishments.

The elderly are bearing the brunt of the epidemic in Spain, with 67 per cent of deaths from Covid-19 involving patients over 80.

The discovery of the bodies came as Spanish health workers begged the government for help after shocking video emerged of patients lying on the floor of an overwhelmed hospital in Madrid.