Travellers to Germany from Nigeria and dozen other countries deemed high-risk, such as the United States of America, Egypt, Souith Africa, Brazil and Turkey, will have to to take a Covid-19 test or face a €25,000 fine.
The German government said travellers arriving in the country from Saturday could be fined if they do not take the test within 72 hours.
The switch to mandatory testing comes after voluntary tests were introduced at airports weeks ago.
Travellers have the option of getting tested through private means within the allotted time period if they prefer.
Most countries in Africa and Asia are also on the list, as well as Israel and Luxembourg.
Germany, which has been one of the countries to most successfully navigate the coronavirus crisis, has seen its number of cases rise in the past week following a staggered re-opening of schools.
The daily infection rate has exceeded 1,000 for the first time since May, an increase that comes amid fears of a second wave of infections across Europe.