'Pokemon Go' developer Niantic have admitted "technical issues" were partly to blame for problems at the game's festival.

Pokemon Go

Pokemon Go

Niantic CEO John Hanke admitted "oversaturation" of mobile data networks were also responsible for the difficulties suffered by some who attended the Chicago-based event to mark the one-year anniversary of the title.

He wrote in a statement: "Technical issues with our game software caused client crashes and interfered with gameplay for some users. The gameplay issue was resolved with a server configuration change and the crashes were also addressed for many but not all users.

"A more protracted problem was caused by oversaturation of the mobile data networks of some network providers.

"This caused many attendees to be unable to access Pokémon GO or other Internet services. Network congestion also led to a login issue which affected some users able to access the Internet. This latency-related login issue was addressed with a second Niantic configuration change (sic)."

Niantic have issued an apology to fans and gave full refunds as well as $100 in PokeCoins to make up for the disappointment.

John added: "Early in the afternoon we informed players that we would refund tickets to those who wanted it and would grant $100 USD in PokéCoins to all attendees due to the inconvenience.

"We also released the 'unique' Pokémon spawning at the event to the surrounding neighbourhoods to give people a way to catch them where the mobile network was stronger."

'Pokemon Go' trainers from all over the world were encouraged to attend the event to meet fellow players and share their experiences of playing the title.