Japan will impose tougher rules on athletes and staff participating in the Tokyo Olympics from countries hit by the highly contagious delta variant of the coronavirus, including more rigorous testing and restrictions on coming into contact with other people, the government's top spokesman has said.

The move comes amid concerns the games, set to start July 23, could become a superspreader event. The capital is already seeing infections creep back up just a week after a state of emergency was lifted.

Athletes and staff will be required to be tested every day for a week before coming to Japan, during which time they are to self-isolate, Chief Cabinet Secretary Katsunobu Kato said at a news conference Monday. They will also be forbidden from coming into contact with other people for three days after arriving.