The two bonus missions available as pre-order DLC for Alien: Isolation will also be available to download separately after release, Creative Assembly has confirmed.

The developer's response follows concern from fans about the decision to lock the content behind pre-orders and make one of the missions exclusive to particular retailers, prompting an online petition against the move.

But despite the criticism, Creative Assembly said that it had been "genuinely been great to see the reaction to The Crew Expendable and Last Survivor pre-order bonus content we announced yesterday and how excited you all are to re-experience those classic scenes from the original movie with our Alien. It's been absolutely amazing for us at the Studio.

"However, some of you have been asking if the two pieces of content are only available through pre-order or if we'll be releasing them at a later date as well. So, I can confirm today that we do plan to release both Crew Expendable and Last Survivor at a later date and we'll have more details for you guys on that shortly."

The two missions will let players able to relive key scenes from the original Alien movie and sees the original cast - including Sigourney Weaver - return to lend their voice and likeness to the characters.

It isn't clear whether SEGA intends to charge for the content when it releases separately.

Alien: Isolation launches this October on Xbox One, Xbox 360, PlayStation 3, PlayStation 4 and PC.