Foreign researchers received recently by a Japanese government-affiliated institution are having to follow stricter COVID-19 quarantine rules than otherwise and have been "jailed" in their hotel rooms since their arrival in Japan, people with knowledge of the situation said Wednesday.

Over 50 researchers on a program by the Japan Foundation are not allowed to leave their rooms at all for up to 15 days following their arrival in Japan and security guards are on watch to catch rule-breakers, sources said.

The scholars arrived in Japan on Oct. 28 and are staying at a hotel close to Narita Airport near Tokyo for quarantine.