Upcoming RTS StarCraft II will be sold as three separate games, Blizzard has revealed.

At the company's recent BlizzCon event, it revealed that the single-player campaign of the hotly anticipated follow-up to the still popular StarCraft will be divided into three products reflecting the game's three races - Terran, Zerg and Protoss. The first game in the series will be Terran: Wings of Liberty, followed by Zerg: Heart of Swarm and Protoss: Legend of the Void.

Some fans have reacted angrily to the announcement, and expressed concern that they will be charged three times for the same game.

Blizzard told Kotaku, that fans should think of each game as an expansion, like Warcraft III's The Fozen Throne or StarCraft's Brood War.

Each new game will come with upgrades and changes to the multiplayer, as well as a fully realised campaign. The initial campaign will feature Terran Jim Raynor, with a meta-game that involves upgrading technologies. The second, featuring the Zerg, will have a meta-game involving diplomacy.

According to StarCraft II lead producer Chris Sigaty, Blizzard decided to launch the game in three parts because it got bigger than they expected and to include all three campaigns from the get go would have delayed the game for years.

Details on pricing and dates are unknown.