UK traveler heading towards Portugal will have to quarantine for 14 days unless they can present proof they had been fully inoculated a fortnight before their arrival.
The Portuguese government added the UK to the list of countries from which travelers must quarantine “at home or a place indicated by the health authorities”.
The rules came into effect at midnight.
Hong Kong has also prohibited all passenger flights from the UK from 1 July. The Hong Kong government said the UK had been added to its “extremely high-risk” group.
A government statement said cases imported from the UK “involving variant virus strains” had been “persistently” detected in the past few days.
Spanish Prime minister Pedro Sanchez has also announced UK travellers will either need to prove they are fully vaccinated, or provide a negative PCR test on arrival in the country.
The change, which will come into effect later this week, comes after Spain revealed in May it was lifting all restrictions for British visitors, who represent the country’s biggest single foreign tourism market.