Japan plans to tighten its border control to prevent the spread of more contagious variants of the novel coronavirus, asking travelers from Vietnam and Malaysia to stay in government-designated facilities for six days after arrival, government sources said Monday.

It will also set the quarantine period at such facilities at 10 days for travelers from Afghanistan and three days for those from Thailand and some U.S. states, the sources said.

Japan has already imposed a travel ban on 159 countries and regions, restricting entry of foreign nationals, including those with resident status, who have been to those countries within the past two weeks, except under special circumstances.