Activision says their wildly successful first-person shooter Call of Duty: Modern Warfare 2 has crossed the $1 billion mark in global sales, citing internal estimates.

In its opening month, the game sold 6 million copies in the U.S. alone, according to figures from NPD Group.

"There are only a handful of entertainment properties that have ever reached the $1 billion mark, which illustrates the power of the Call of Duty franchise and mass appeal of this game," says Activision CEO Bobby Kotick in a statement.

Modern Warfare 2 set numerous sales records after launching November 10. In the North American and U.K. markets, the game sold 4.7 million on its first day. Activision revealed the latest installment of the military franchise set an entertainment industry record by raking in $550 million in its first five days.

Readers, still playing Modern Warfare 2?

By Brett Molina