In Chicago, one of America's most violent cities, drug arrests have plummeted 42 per cent in the weeks since the city shut down, compared with the same period last year.

Part of that decrease, some criminal lawyers say, is that drug dealers have no choice but to wait out the economic slump.

"The feedback I'm getting is that they aren't able to move, to sell anything anywhere," Chicago criminal lawyer Joseph Lopez said.

Overall, Chicago's crime declined 10 per cent after the pandemic struck, a trend playing out globally.

Cities are reporting stunning crime drops in the weeks since measures were put into place to slow the spread of the virus.

Even among regions that have the highest levels of violence outside a war zone, fewer people are being killed and fewer robberies are taking place.

Still, law enforcement officials worry about a surge of unreported domestic violence, and what happens when restrictions lift - or go on too long.

Across Latin America, crime is down to levels unseen in decades.

El Salvador reported an average of two killings a day last month, down from a peak of 600 a day a few years ago.

Much of the decrease has taken place because of tougher security policies and gang truces.

But the imposition of near-total limits on movement is likely driving it down further, according to analysts and national statistics.

In Peru, where crime levels fell 84 per cent last month, Lima mortician Raul Gonzalez usually has as many as 15 bodies a day - many are homicide victims.

This week he napped on a bench after six hours without a client.

"There are almost no killings or car accidents these days," Gonzalez said.

In South Africa, police reported a stunning decline during their first week of lockdown measures.

Police Minister Bheki Cele said reported rapes were down from 700 to 101 over the same period last year.

Serious assault cases plummeted from 2673 to 456, and murders fell from 326 to 94.

The US virus epicentre in New York saw major crimes - murder, rape, robbery, burglary, assault, grand larceny and car theft - decrease by 12 per cent from February to March.

In Los Angeles, 2020 key crimes statistics were consistent with last year's figures until the week of March 15, when they dropped by 30 per cent.

Former New York Police Department sergeant Joe Giacalone said there's far fewer opportunities for criminals to take advantage of.

"Most burglars, they wait for you to leave the house," he said.

Australian Associated Press