Nintendo just announced it via PR. That include download sales, by the way, so it's actually 1m units sold... (PR is actually a bit ambiguous, as it says 1m sold in the title, but ends with 1m units shipped...)
4th game to reach 1m during first week, after Youkai Watch 2, Monster Hunter 4 and Pokémon X/Y.
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4th game to reach 1m during first week, after Youkai Watch 2, Monster Hunter 4 and Pokémon X/Y.
Source