An aerial view of coffins being buried at an area where new graves have been dug at the Parque Taruma cemetery during the COVID-19 pandemic in Manaus, Brazil on Tuesday. Graves are being dug at a new area of the cemetery for suspected and confirmed victims of the coronavirus pandemic. Photo: AFP

US President Donald Trump partially blocked immigration to the US "to protect American workers" from the economic shock of the coronavirus, as the United Nations (UN) warned the world was facing "a humanitarian catastrophe."

The UN alarm bells came as nations scrambled to not only fight the virus - which has killed 178,000 people and infected more than 2.5 million - but also desperately seek ways to limit the vast damage unleashed on the global economy.

With more than half of humanity under some form of lockdown, businesses shuttered and millions of jobs lost, the world is facing its worst economic downturn since the Great Depression and the UN's World Food Programme (WFP) said it would hit the least privileged the hardest.

"I want to stress that we are not only facing a global health pandemic, but also a global humanitarian catastrophe," the WFP Executive Director David Beasley told the UN Security Council on Tuesday.

"Millions of civilians living in conflict-scarred nations... face being pushed to the brink of starvation."

The WFP warned the number of people suffering from acute hunger was projected to nearly double to 265 million in 2020.

In the US, where the economy is reeling and 22 million people have lost their jobs, Trump said he would stop the issuing of green cards for 60 days, but exempt temporary workers such as seasonal farm laborers.

The US is the hardest-hit country in the world, with over 45,000 deaths and more than 820,000 coronavirus infections, and healthcare infrastructure in major hotspots like New York City has struggled to cope.

In Europe, some countries have started easing lockdowns as the spread of the virus is slowly brought under control, but the cancellation of some of the world's best-known events served as a reminder that the pandemic is far from over.

In Germany, where small shops have been allowed to reopen, authorities canceled this year's Oktoberfest, the beloved beer-swilling festival in southern Bavaria, for the first time since World War II.

Spain, which is set to allow children some movement in a week, said it was scrapping the annual bull-running festival in Pamplona.

Russia reported 57,999 coronavirus cases and 513 fatalities, and Russian President Vladimir Putin has warned that the peak has not yet passed.

The pandemic has ripped apart the global sports calendar, forcing most notably the postponement of the Tokyo Olympics to 2021.

German football authorities are expected to announce plans on Thursday for its top-level league to restart matches in empty stadiums on May 9.

However, the Dutch football federation said it intended to end its season because of the extension of a ban on large gatherings.

AFP