Two cities known for ninja, Iga in Mie Prefecture and Koka in Shiga Prefecture, have been officially named "Japan Heritage" properties, the government said Friday.

The move is part of a larger effort to designate 17 new categories of cultural assets to increase tourism ahead of the 2020 Tokyo Olympics.

The pair of cities known for two of Japan's most famous ninja clans were included in the third batch of so-called Japan Heritage properties, the Cultural Affairs Agency said.

The government has been recognizing tangible and intangible cultural assets in regional areas to showcase historical events and popular traditions under a 2015 project aimed at revitalizing local economies through tourism. The assets are grouped according to historical stories and traditions to make it easier for tourists to understand.

Also added to the list was a set of cities and towns known as ports for kitamaebune cargo ships that sailed along the Sea of Japan coastline during the Edo Period (1603-1868) and the Meiji Era (1868-1912).

Other assets include famous silk-producing centers: Yamagata Prefecture and Yabakei Gorge in Oita Prefecture.

The certification of 17 new categories of cultural assets this year brings the number of designation sites to 54. The agency aims to choose 100 sites before the 2020 Games.

The agency will provide financial assistance to municipalities and prefectures as part of the effort to draw more visitors. Such aid includes setting up multilingual websites and training volunteer guides.

The third batch of Japan Heritage assets was chosen from a total of 79 proposals made by municipalities earlier this year.