Prime Minister Justin Trudeau says any Canadian planning an international trip should cancel it.
Trudeau is warning that while Canadians have the right to travel, the government could at any time, and without warning, enforce new restrictions on travellers returning to Canada.
New variants of the virus that causes COVID-19 add a level of uncertainty that could affect decisions about how to handle international arrivals.
The Public Health Agency of Canada has documented 183 flights arriving in Canada from abroad since Jan. 4 alone, on which at least one passenger had COVID-19.
That includes four flights from London since the ban on incoming flights from the United Kingdom was lifted Jan. 6.
Trudeau would not say when pressed what other measures he is considering, noting only that travellers now must present negative COVID-19 tests before boarding their planes, and still must quarantine for two weeks after arriving.