Pokemon Go mania is sweeping over the United States as players armed with smartphones are out hunting in the streets, parks, and rivers of their cities to capture monsters and gather supplies in the hit game. The "augmented reality" game, based on the 1990s Japanese franchise, has become an overnight sensation with U.S. fans.

The mobile game surged to the top of Apple Inc's app charts over the weekend and sent gamers out to the streets of major cities looking for virtual Pokemon characters to capture.

"I think it's a great idea because, like, you get to go out and meet new people and interact. Like right now, I met a couple of guys playing Pokemon, so we kind of just talked and stuff like that, so I think it's great," said Henry Mendez, Pokemon Go player.

"It's a fun, easy game that everyone can relate to, people that have never touched Pokemon or even played, like, any of the cards or any of the games are like, all right, it seems kind of cool, I can play this anywhere, from my home," said player Freydo Cavero.

"I started playing this, like, three days ago. I went to Little Tokyo and I pretty much went around, it was, like, midnight. There were over, like, a hundred people just playing Pokemon. And people just passed by and just asked what were we doing and we said, oh, we're just texting each other, but we were just playing Pokemon Go," said player Jessica Crawford.

Gamers use their mobile devices to find and capture virtual characters such as cuddly yellow Pikachu at various real-life locations.

Five days after its release, the game's rate of daily active users was neck and neck with Twitter, according to the analytics firm SimilarWeb. The popularity of the game has even been driving sales of Pokemon merchandise.

"When Pokemon Go released a couple of days ago, all our hats are selling out in Pokemon, all our plushies are selling out. Everyone wants to just accessorize for the game, I guess," said Rachel Grady, "Anime Jungle" sales assistant.

Pokemon Go was released last week in the U.S., Australia and New Zealand. A tidal wave of interest in the game has bogged down servers hosting the software, which is frustrating some players and delaying plans to launch Pokemon Go in more countries.

After Pokemon Go took off, Nintendo's shares surged nearly 25 percent for their biggest daily gains in history.