TOKYO (AFP) - A Japanese university is planning what it says will be the world's first research centre devoted to ninjas - the black clad assassins known for secrecy and stealth.

While mostly confined to history books and fiction, ninjas have been enjoying something of a resurgence as the Japanese authorities increasingly deploy them to promote tourism ahead of the 2020 Olympic Games in Tokyo.

Now, Mie University in central Japan - the region considered the home of the feudal martial arts masters - has announced that a ninja research facility will be established in July.

It plans to compile a database on ninjas and encourage cooperation between scholars from different disciplines who study ninjas, according to Dr Yuji Yamada, a professor of Japanese history at the university.

"We'll conduct research on ancient documents and collaborate with science researchers to be able to apply the wisdom of ninjas to modern society," Dr Yamada, who is setting up the centre, told AFP on Thursday (May 11).

"For instance, ninjas burned Japanese incense before going out to avoid evil things. We assume the incense could boost concentration and thus ninjas could avoid injuries," he said, adding that research on such fragrances might prove useful in today's world.

The facility will be located in Iga - 350km south-west of Tokyo - a mountain-shrouded city that was once home to many ninjas.

Dr Yamada also said the centre plans to publish its research in English as well as Japanese so as to make it accessible for interested researchers and fans overseas.

Amid the ongoing ninja boom, Aichi prefecture last year began hiring full-time ninjas, including a foreigner, to promote tourism in the area known for the historic Nagoya Castle.

In 2015, governors and mayors from prefectures around the country traded their usual suits for ninja costumes to announce the launch of a "ninja council".