It's possibly the biggest evangelism opportunity of the millennium.

Church leaders are adopting the Pokémon slogan in aid of their own evangelism: "Gotta catch 'em all" as thousands of Pokémon Go players turn up on their doorsteps.

The "augmented reality" gaming phenomenon, which has added up to $9 billion to the value of Nintendo since it was released just days ago in the United States, New Zealand and Australia, has given an unexpected boost to churches.

Churches have not always been greatest fans of the distinctive pocket monsters such as Pikachu and the "legendary" Rayquaza. But that is changing as fast as a player can catch a Pidgey on their mobile phone.

The wireless geo-location technology used in the game means many "gyms" and "Pokéstops" are church buildings.

And it is the rare millennials, the missing generation in many churches, who are turning up at churches across America and Australia in swarms to catch Pokémon and do battle for control of gyms.

If UK phones are reset to the United States, the game can also be played in Britain, which has led to a Methodist church in Birmingham being identified as one of the UK's first known PokéStops after players started turning up. The City Road church has now posted new signs advertising its 11am Sunday service: "Pokémon Go Gym, you are welcome - Jesus Cares About Pokémon Gamers".

A Presbyterian church in San Diego organised a free church lunch with a Pokémon "lure" event. The church wrote on Facebook: "We'll be setting lures tomorrow from 12-1 at our pokestop (church sign). Come by our sidewalk to catch Pokemon, get free lunch and maybe even take control of our Pokemon Gym (Sanctuary)."

One US church put on its sign: "We are a poke stop. Get supplies outside, find Jesus inside."

Millennial evangelical blogger Chris Martin tweeted: 

The Wardrobe Door blogger listed eight ways churches can capitalise on the game. "Every church we drove past this weekend was a PokéStop or gym—from a gigantic megachurch to a tiny fundamentalist church," he wrote. "This has lead to some interesting situations for many unchurched gamers. Some exclaimed how this would be the first time in years they have been to a church."

He urges churches to find out whether they are a PokéStop or a gym, as that will affect how long people hang around the building, and then to staff the area with a greeter who knows how to play the game. He advises them to tweet the fact they are a gym, as the subject has been trending since the game's launch, to offer free gifts and put on trading nights.

He writes: "Pokémon Go is providing churches with an opportunity to meet new, unchurched people from their neighborhood. You can form relationships with non-Christians just by walking outside your church. Don't miss out on this because it's not something you are interested in. Paul said he became all things to all people so that some might come to Christ.

"Pastors and church leaders can make fun of Pokémon Go and the players walking right outside their doors. Or they can take Paul's advice and become a gamer to reach the gamers for the sake of the Gospel."