Pro-Isis social media accounts have been celebrating the Manchester Arena bombing online.
22 people died and up to 59 were injured after a suicide bomber struck crowds leaving a concert by US singer Ariana Grande.
Isis supporters on Twitter have been reveling in "the bombs of Raqqa and Mosul coming back to Manchester."
They have called the incident a "victory" against the West.
In one video, a supporter of the group addresses the camera in English, saying the attack was "only the beginning".
A terrorism analyst, Michael S. Smith II, also claimed several groups to be celebrating the attack might be an indicator of the caliphate being behind it.
Despite this, there has been no official claim of responsibility - yet - from any terrorist group.