Japan said Tuesday it will strengthen border controls to keep new coronavirus variants at bay by requiring its citizens and resident foreigners returning from another 13 mostly European countries to go through additional quarantine measures.

Returnees from the 13 countries where new virus variants are feared to be spreading will be newly asked to stand by at a designated facility after arrival for a retest for the virus on the third day after entering the country, effective Friday.

The new requirement will be added to the current measures of turning in negative testing results within 72 hours of departure and taking a coronavirus test upon arrival.

The 13 countries are Austria, Belgium, Brazil, Denmark, France, Germany, Italy, the Netherlands, Nigeria, Slovakia, Sweden, Switzerland and the United Arab Emirates.

The countries join Ireland, Israel, Britain and South Africa, along with Brazil's Amazonas state, that have already been subject to the strengthened quarantine measures for concerns over spreading new coronavirus variants.

Even if negative in all the coronavirus tests, using public transportation will be prohibited until completing the rest of the 14-day self-quarantine period.

Japan currently bans all entries of nonresident foreigners except for those given approval under "special exceptional circumstances."