The Japanese government said Thursday it will tighten border controls for visitors from Costa Rica, the Dominican Republic and Namibia in response to the spread of the highly contagious Delta variant of the novel coronavirus.

In a new set of border control measures to take effect Sunday, visitors from the three countries as well as the Republic of Sakha in eastern Russia will be asked to stay in designated facilities for three days after arrival and be subject to more coronavirus testing, according to the Foreign Ministry.

Travelers from Moscow will also be required to observe a six-day quarantine in designated facilities, up from three days, and take additional tests on the third and sixth days under the new measure.

Meanwhile, those from Latvia, Switzerland and Vietnam will no longer be asked to stay in designated facilities if their test results upon arrival are negative but are still requested to undergo self-isolation for 14 days after entering Japan.

Related coverage:

Japan to tighten border control for travelers from Indonesia, Zambia

Japan to require stricter quarantine of travelers from Indonesia, Uganda

Japan eyes tougher Olympics rules for Delta variant-hit countries