A two-week ban on foreign travel took effect in Portugal on Sunday as the country grapples with the worst surge in Covid-19 cases anywhere in the world.
The few exceptions include international professional activities, medical emergencies, goods transport or to reunite families, the interior ministry has said.
According to AFP data, Portugal is the world's worst-hit country relative to its population of about 10 million.
Nearly half of the 12,000 Covid-19 deaths have occurred in January alone during a third wave of the virus, and Portugal went into a second general lockdown on January 15.
Border controls have been re-established at land routes into Portugal's only neighbour Spain, at a reduced number of crossing points.
At Elvas, one of the main border crossings some 200 kilometres (120 miles) east of the capital Lisbon, police and customs officials checked dozens of motorists Sunday morning, an AFP journalist saw.
For air travel, Lisbon has set different criteria for flights arriving from fellow EU countries and the Schengen area depending on the severity of the virus situation in each nation.
Passengers from less affected countries such as Norway are not restricted, while those from countries with situations deemed intermediate, like France, must show negative Covid-19 tests conducted less than 72 hours before boarding.
Worse-hit countries such as Spain and Ireland must additionally observe a 14-day quarantine from the date of arrival in Portugal.
Portugal has also suspended all flights to Britain and Brazil because of new, more contagious variants originating in the two countries.