Direct humanitarian and repatriation flights will still be authorised but passengers must present a negative Covid-19 test taken 72 hours before departure and quarantine for 14 days.
The measures are due to be reviewed on March 16.
Portugal's tourism minister told the BBC on Friday the country hoped to allow British tourists who could prove they had tested negative or were immune to Covid-19 into the country from May 17, when England lifts its ban on international travel.
Portugal, which has so far reported 808,405 Covid-19 cases and 16,486 deaths, is set to begin a sector-by-sector lifting of restrictions next week after nearly two months of strict lockdown after a devastating surge in cases at the beginning of the year.