According to a statement sent directly from Blizzard, all gamers in Iran are being restricted from signing into Battle.net, and will no longer be able to play any of Blizzard games for the foreseeable future.
Last week some Iranian players started reporting sign-in difficulties, but it has only recently become apparent that these issues are the direct result of US policies, intendeded to restrict American companies from dealing directly with Iran.
"We can't speak to reports surrounding the Iranian government restricting games from its citizens... United States trade restrictions and economic sanction laws prohibit Blizzard from doing business with residents of certain nations, including Iran," read the statement. "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."
Blizzard is claiming that very few subscribers will be affected, but multiple threads on Blizzard's official forums suggest that a great number of gamers are understandably upset at being blocked from using Blizzard products for political reasons. At time of writing no refunds were being offered.