Canada has closed its borders to all foreign nationals except US citizens and permanent residents, with Prime Minister Justin Trudeau urging people to stay at home to help stem the spread of the new coronavirus.
"We will be denying entry into Canada to people who are not Canadian citizens or permanent residents," Trudeau told reporters at a news conference outside his home, where he is under quarantine.
"All Canadians should stay home."
The death toll in Canada jumped to four on Monday, from one on Sunday. All three new deaths were reported by the Pacific province of British Columbia.
Health officials say they have found about 350 cases of Covid-19 across all 10 provinces.
Trudeau acted after the premiers of the two most populous provinces - Ontario and Quebec - urged him to clamp down on the borders.
"As the virus continues its spread, we've decided to take increasingly aggressive steps to keep you and your family safe," he said, adding that trade would not be affected.
Canada shares a long unguarded frontier with the United States, which takes 75 percent percent of Canadian goods exports.
Asked why US citizens were exempt, Trudeau said the close bilateral integration meant the United States was in a different category from other nations but added that more measures could be announced soon.
Trudeau said Canadians should not travel outside the country and urged citizens who were abroad to return home. He also said Canada would reroute all international flight arrivals to four airports - Toronto, Calgary, Montreal and Vancouver.
Canada has also imposed tougher screening requirements.
The Canada Border Services Agency said all travellers arriving from any international destination would now be told to self-isolate for 14 days.
Some visitors who flew into Canada over the weekend told reporters they had not undergone any screening.
Ontario, which accounts for nearly half of the confirmed cases, said it would delay its 25 March budget and instead deliver an economic and fiscal update.
"These are unprecedented times ... the reality is, we're facing some tough waters ahead," said Ontario Premier Doug Ford.
Trudeau has said his Liberal government will soon announce a major stimulus package to help those hit economically by the outbreak.