The police have enhanced security at various locations, including airports and main train stations, in preparation for the Group of Seven summit scheduled for May 19-21 in Hiroshima.
They have increased patrols of so-called soft targets, which are defined as sites where significant numbers of the general public have easy access.
On Friday, a large number of uniformed officers patrolled Haneda Airport in Tokyo, inspecting waste cans for suspicious objects and examining the runways with binoculars.
In 2005, when a summit was held in Britain, terrorist attacks occurred approximately 600 kilometers away in London.
A senior police official stated, “Anywhere in Japan could be a target.” “[Police] nationwide will be on high alert.”