The NPD announced the US sales charts for March 2014, and analyst David Gibson provided some additional details from Konami on Twitter.
Metal Gear Solid V: Ground Zeroes managed to sell 278.000 copies in the US last month. This lands the game at the sixth place in the sales charts. Of that number, 204.000 are for PlayStation 4 and Xbox One.
The game sold 304.000 copies in Japan. All these numbers only account for retail sales, as digital sales are unknown at this moment.
European numbers are still unknown, but we do know the game did well in some individual countries.
Source: David Gibson Twitter, Gametrailers