Sydney/Wellington: Growing numbers of Pokemon Go players in Australia, one of three countries where Nintendo Co's smash-hit mobile game is available, are complaining they're having trouble logging in, raising concerns the Japanese firm may not be able to roll the game out globally as quickly as planned.

Shares in Nintendo fell nearly 6 percent in Tokyo early on Wednesday after a three-day surge on the successful U.S. launch of the augmented reality game last week added 1.2 trillion yen ($11 billion) to the company's market value. Based on the 1990s Japanese franchise, the augmented reality game topped Apple
Inc's free app charts.

By 0220 GMT on Wednesday, a total of about 1,300 Pokemon Go users had reported problems accessing the game in Australia over the last two days, according to website, which tracks digital service disruptions.

The game has only been released in the United States, Australia and New Zealand, and Nintendo has said launches for other countries including Japan - one of the world's biggest gaming markets - are due soon.

Both Nintendo and Niantic, which developed the game in tandem with Pokemon Co, declined to comment. Nintendo owns a third of Pokemon Co and has an undisclosed stake in Niantic.

Some gamers in Australia have speculated servers were overloaded because players in the United Kingdom, where the game is not yet available domestically, were trying to log on.

"When Pokemon Go servers experience issues, so do I," a user with the handle @_emilymcc wrote in a post on the website. The reported disruption adds to a flurry of headaches Nintendo is facing with Pokemon Go. Security researchers raised concerns about the vulnerability of users' data after finding that Pokemon Go players signing into the game via a Google account on an Apple operating system device unwittingly gave "full access permission" to Google accounts.

Meanwhile cases of armed robberies and injuries involving Pokemon Go players have also been reported.