The first death came in the central Chinese city of Wuhan on January 9.

It took 83 days for the first 50,000 deaths to be recorded and just eight more for the toll to climb to 100,000.

It took another eight days to go from 100,000 to 150,000.

The death toll is still far short of the so-called Spanish flu, which began in 1918 and is estimated to have killed more than 20 million people by the time it petered out in 1920.

China, confirming long-held suspicions, acknowledged on Friday that the coronavirus death toll in the one-time epicentre city of Wuhan was higher than reported, adding 1290 fatalities to total more than 4600.

In Italy, Spain, Britain, the United States and elsewhere, similar doubts emerged as governments revised their death tolls or openly questioned the accuracy of them.

Authorities say that almost everywhere, thousands have died with COVID-19 symptoms - many in nursing homes - without being tested for the virus, and have thus gone uncounted.

"We are probably only seeing the tip of the iceberg," said Barcelona University epidemiologist Antoni Trilla, who heads the Spanish government's expert panel on the crisis.

Spain's 17 autonomous regions have been ordered to adopt uniform criteria on counting the dead. The country has recorded more than 19,000 deaths but the system leaves out patients who had symptoms but were not tested before they died.

In Italy, where the official toll has climbed past 22,000, a government survey released on Friday of about one-third of the country's nursing homes indicated that more than 6000 residents have died since February 1. It was unclear how many were a result of COVID-19.

In Britain, with an official count of about 14,600 dead, the country's statistics agency said the actual number could be around 15 per cent higher. Others think it will be far more.

The official death toll in New York City - the hotspot of the US - soared by more than half earlier this week when health authorities began including people who probably had COVID-19 but died without being tested. Nearly 3800 deaths were added to the city's count.

"There is a general feeling that the epidemiologists don't have a clue of what's going on, that experts know even less and that governments are concealing information, but I don't think that's true," said Hermelinda Vanaclocha, an epidemiologist on Spain's top virus advisory panel. "It's simply not easy."

Such figures can have a huge influence on governments' actions, as medical workers struggle to figure out how to cope with surges of sick people and officials make crucial decisions about where to devote resources and how to begin easing lockdowns to resuscitate their economies.

Australian Associated Press