Nintendo shares spiked over 8 percent Tuesday after the company's first mobile app, Miitomo, racked up a million users in three days.

Miitomo was released last Thursday and over the weekend, the official Twitter account for the app announced the grand total. Miitomo, which is only currently available in Japan, was also number one on Apple's App store in the country, according to analytics firm App Annie.

Tuesday is the first trading day back in Japan after a public holiday and Nintendo investors reacted positively to the news. Mobile is seen as a key part of Nintendo's strategy for the future and has been a big focus for the company over the past year.

Last March, Nintendo struck a partnership with mobile firm DeNA to help with its push into smartphone apps and games. Miitomo was developed alongside DeNA and allows players to create characters known as a Mii. While it is more of a social app rather than a game, analysts said the 1 million users generated in such a short space of time shows that Nintendo can be a big success in mobile when it brings its better known characters such as Mario onto the small screen.

"Just imagine what a Nintendo game could do for this company," Serkan Toto, chief executive of game industry consultancy Kantan Games, told CNBC by phone.