Blizzard Entertainment will release the Diablo II Expansion Set next year, the company has announced.

Diablo II has sold over two million copies since it shipped last month. The Expansion Set will include two new character classes (Assassin and Druid), and a series of fresh quests and challenges. Also, a level set in the Barbarian Highlands will be added.

The Expansion Set will offer new monsters and level bosses, siege towers and thousands of new weapons, armour and magical items.

Mike Morhaime, Blizzard’s president, said: "The success of Diablo II has been overwhelming."