Techland has revealed brand new details on Dying Light's upcoming expansion pack 'The Following', confirming that the DLC will introduce a brand new campaign and an additional 10+ hours of gameplay.

Completing everything in the DLC may even take some players up to 20 hours, the developer says.

The base game, meanwhile, has already sold over 5 million units since launching on PS4, Xbox One and PC in January, a milestone which Techland describes as a "tremendous success".

"To be honest, I think even we are a little surprised by the scope of our success," producer Tymon Smektala told VideoGamer.com at last week's Gamescom. "We knew that we'd made a good game. If you are a gamer, even if you make games you are still a gamer, so we know the game is good when you feel that rush when you play.

"So we knew that Dying Light is a good game, we know it's going to be successful, but that successful? We are in the 10 best-selling games in the US right now for the first half of the year, so tremendous success. More than 5 million copies sold."

Dying Light's success resulted in Techland halting development on first-person hack & slash Hellraid earlier this spring to focus its resources on the zombie IP. The studio is currently experimenting with ideas for a sequel, which it suggests could be too ambitious for PS4 and Xbox One.