LONDON (AP) — They've vanquished elves, trolls, and all manner of magical monsters. But one select group of online gamers is facing an even more formidable foe: The U.S. sanctions regime.

Iranian players of "World of Warcraft," the massively popular online multiplayer franchise, have found themselves frozen out by Blizzard Activision Inc., the American company behind the game. Iranian role playing enthusiasts have spent much of the past week peppering Blizzard's message board with complaints about how they weren't able to log on to the service — only to be told recently that U.S. law was to blame.

"United States trade restrictions and economic sanction laws prohibit Blizzard from doing business with residents of certain nations, including Iran," the company said in an email sent to players last week and forwarded to The Associated Press late Tuesday. "Blizzard tightened up its procedures to ensure compliance with these laws, and players connecting from the affected nations are restricted from access to Blizzard games and services."

A post to Blizzard's message board by a company employee also noted that rules meant Iranian players would not be getting refunds.

Blizzard's "Warcraft" franchise dates back to 1994 and has grown into a sprawling virtual world complete with its own online economy and a thriving subculture. The games' more than 9 million subscribers can log on to assume the identity of a dizzying array of fantastical characters and fight together — or each other — for experience, magical weapons, and loot.

It wasn't clear precisely how many players were affected by the block. Blizzard's public relations director, Rob Hilburger, said that the company doesn't break player data out by country or region for competitive reasons. But he said the Iranian market compromised only "a tiny fraction" of the company's subscribers worldwide.

Hilburger didn't immediately respond to a question asking why the company had only recently blocked Iranian players from its service.

The United States and its allies have been steadily increasing economic pressure on Iran as it tries to convince the Islamic republic to open up about its disputed nuclear program, which Western governments fear is a cover for the development of atomic weapons. Tehran insists the program is intended for civilian energy generation.

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Blizzard's guide to "World of Warcraft": http://us.battle.net/wow/en/game/guide/

Raphael Satter can be reached at: http://raphae.li/twitter

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