"Everyone at MI5 is revolted by the disgusting terrorist attack in Manchester last night. Our hearts go out to the families of the victims, the injured and everyone affected by it. Our teams have been working with the police through the night to assist the investigation. We remain relentlessly focused, in numerous current operations, on doing all we can to combat the scourge of terrorism and keep the country safe," the statement on MI5's website read.
At least 22 people, including children, were killed and almost 60 injured when a blast rocked through the Manchester Arena foyer after US singer Ariana Grande finished performing her concert at the venue on Monday night.
UK police have confirmed the attack to be an act of terror performed by one person, who died after detonating an explosive device.