With more than 1.2 million people infected with the coronavirus, the UN chief has appealed for "peace at home" out of concern domestic violence was rising as the social and financial toll of the pandemic deepened.
US officials warned of sad developments to come in the worst-hit country, where medical supplies were short and morgues crowded.
UN Secretary-General Antonio Guterres described "a horrifying global surge in domestic violence" in recent weeks.
"For many women and girls, the threat looms largest where they should be safest - in their own homes," Gutteres said in his statement. "And so I make a new appeal today for peace at home - and in homes - around the world."
"I urge all governments to make the prevention and redress of violence against women a key part of their national response plans for COVID-19," he said.
In Japan, reports say Prime Minister Shinzo Abe plans to declare an emergency in Tokyo and other cities on Tuesday. His government is also expected to announce a 60 trillion yen ($A921 billion) economic package to fund coronavirus measures and support businesses and jobs.
Japanese officials say they cannot enforce a hard lockdown as in China or parts of Europe. Most of the measures would be requests and instructions, and objectors would not be punished.
Japan has more than 4000 cases, with more than 80 deaths.
In the US, the nation's top doctor warned many would face "the hardest and saddest week" of their lives while Britain assumed the unwelcome mantle of deadliest coronavirus hot spot in Europe after a record 24-hour jump in deaths that surpassed even hard-hit Italy's.
British Prime Minister Boris Johnson was hospitalised for tests after continuing to have symptoms of COVID-19. Downing Street says the hospitalisation is a "precautionary step" and he remains in charge of the government.
On Monday South Korea's vice health minister, Kim Gang-lip, expressed concerns over loosened attitudes toward social distancing that he says puts the country at potential risk of an infection "explosion."
The country reported 47 new cases of the coronavirus, the smallest daily jump since February 20, but rising infections have been linked to international arrivals as students and other South Korean nationals flock back from the West .
Some hard-hit areas were seeing glimmers of hope - the number of people dying appeared to be slowing in New York City, Spain and Italy. Leaders cautioned, however, that any gains could easily be reversed if people did not continue to adhere to strict lockdowns.
US Surgeon General Jerome Adams offered a stark warning about the expected wave of virus deaths.
"This is going to be our Pearl Harbour moment, our 9/11 moment," he told "Fox News Sunday."
But President Donald Trump later suggested the hard weeks ahead could foretell the turning of a corner. "We're starting to see light at the end of the tunnel," he said at a White House briefing.
In New York City, the US epicentre of the pandemic, daily deaths dropped slightly, along with intensive care admissions and the number of patients who needed breathing tubes inserted, but New York state Governor Andrew Cuomo warned it was "too early to tell" the significance of those numbers.
The outlook, however, was bleak in Britain, which reported more than 600 deaths Sunday, surpassing Italy's increase. Italy still has, by far, the world's highest coronavirus death toll - almost 16,000.
Worldwide, more than 1.2 million people have been confirmed infected and nearly 70,000 have died, according to Johns Hopkins University.
Australian Associated Press