A map expansion pack for Call of Duty 4 has surpassed one million downloads in the first nine days since its release.

The milestone sets a new record for the number of paid downloads on the Xbox Live Marketplace for the Xbox 360.

Xbox Live members clocked up more than 30 million sessions and logged more than 32 million hours of gameplay on the new maps between 4 and 12 April.

"Call of Duty 4: Modern Warfare delivers one of the best online multiplayer experiences ever," said Will Kassoy, senior vice president of global brand management at Activision Publishing.

"We are excited to be able to expand that experience and deliver a new variety of locations and environments which have all the intensity fans have come to expect with Call of Duty."

Call of Duty 4 has sold in excess of nine million units worldwide since its release, making it the best-selling game in unit sales in 2007, according to market watchers the NPD Group, Chart Track and the GFK Group.