The CEO of the 2020 Tokyo Olympics says security is his greatest concern but believes Japan will be safe from the kind of mass street protests currently overshadowing this summer's Rio de Janeiro Games.

"If I had to choose just one challenge from many it would have to be security," Toshiro Muto told The Japan Times in an exclusive interview. "There are many threats of terrorism in the world. It's not just a physical threat, but also the threat of cyberterrorism.

"The level of threat that terrorism poses gets more and more complicated each year. No one knows how sophisticated cyberterrorism will have become by 2020.