The threat levels in the UK listed below are designed to give a broad indication of the likelihood of a terrorist attack, according to MI5. MI5 is responsible for setting the threat levels from Irish and other domestic terrorism. What changes with a critical threat level? How are threat levels determined? VICTIMS IN MANCHESTER BLAST IDENTIFIEDThe international terror threat level scale was only made public in the UK in August 2006, according to the BBC.

Source: Fox News May 24, 2017 20:33 UTC