Emperor Naruhito officially declared his enthronement to world representatives on Tuesday in a ceremony that was conducted amid relative peace and calm.

The last time the event was held, three decades ago, extremists fighting against the imperial system carried out multiple terror attacks.

About 2,000 guests from home and abroad attended Tuesday's ceremony, and some 26,000 police officers were mobilized from across Japan — stepping up security checks and traffic controls around the Imperial Palace and other parts of central Tokyo. An anti-terrorist squad was also deployed to keep watch for threats such as drones in the sky.