Codenamed Exercise Winchester Accord, the training incident began at midnight on Monday 9 May 2016 and was completed on Tuesday morning.
An official video of the exercise sparked controversy after it showed a terrorist entering the building and shouting the Arabic words 'Allahu Akbar' ('God is great') before detonating a suicide vest.
Garry Shewan, assistant chief constable of Greater Manchester Police, released a statement apologising for this aspect of the exercise.
Reaction on social media to the apology was mixed, with many claiming that it was unnecessary, especially as reports emerged of a German man using the phrase before stabbing multiple people at a railway station near Munich.
Others suggested using the language during the training exercise would only succeeded in fuelling racial tensions.
Police Apology Over 'Allahu Akbar' Chants. FFS we're sorry for making the training realistic. How ridiculous is this https://t.co/mmpDB6ZCru— PC Jong Camoron (@PCSouthwest1) May 10, 2016
The police shouldn't have to apologise for using the phrase allahu akbar; it's realistic & has been a precursor to recent terrorist attacks.— Casey Christie (@Casey_Christie) May 10, 2016
Why is he shouting 'Allahu Akbar' ??? Is the point of these terrorist training exercise to help or incite racism? pic.twitter.com/q4fVgNXrcq— 14 days (@behlul_official) May 10, 2016
Sorry if it offends muslims, but suicide bombers do tend to shout 'allahu akbar'— Rob (@Arkhamandcheese) May 10, 2016
Oops sorry for 'Allahu Akbar', but it's too late, already reinforced a dangerous, damaging rhetoric. Disgraceful. https://t.co/EkfZ46Q0qx— Tahmeena Alam (@tahmeenaalam) May 10, 2016