According to the Ministry of the Interior, cited by the Saudi News Agency (SPA), the "temporary suspension" will come into force on 3 February at 9pm local time (6pm in Lisbon).
The countries included in the 'black list' are: Portugal, United States of America (USA), Germany, South Africa, Argentina, Brazil, Egypt, United Arab Emirates, France, India, Indonesia, Ireland, Italy, Japan, Lebanon, Pakistan, United Kingdom, Sweden, Switzerland and Turkey.
Saudi citizens, as well as diplomats and health professionals from these nations are allowed to enter the country, but "within the framework of precautionary measures" recommended by the health authorities, he added.
The formal announcement of these border restrictions follows the warning given by Health Minister Tawfiq al-Rabiah, who warned of the need to impose even more restrictive measures if the Saudi population did not comply with the measures in force until now.
Saudi Arabia has counted 368,000 infections and 6,400 deaths since the beginning of the pandemic. The most populous country in the Persian Gulf (with about 34 million inhabitants) is also the most affected by SARS-CoV-2.
At the beginning of January there were less than 100 daily infections - a figure that contrasts with almost 5,000 in June - but since then health authorities have seen an increase, with another 310 in the last 24 hours.