Manchester- (England) - A blast that rocked the indoors of the Manchester Arena for entertainment, has killed at least 22 people with 59 others being treated at hospital. Terrorist ISIS group claimed the attack. In a statement the group said "Approximately 100 Crusaders Killed and Wounded by Explosive Devices Detonated in Manchesterز" Two children have been identified as the first victims killed in the Manchester Arena terrorist attack. Just in: Police have arrested a 23-year-old man in connection with the Manchester attack Police were called in at the scene at 10:33 PM, London time. It is not clear exactly where the explosion happened but early reports say either at the entrance of the arena or just outside it. Manchester police are treating the incident as a terrorist attack, yet have not disclosed any further information. US Intelligence told Reuters news agency that it is a possible suicide attack considering the venue and the timing of the explosion. "This does not appear to have been a carefully planned attack involving multiple actors, extensive surveillance of the target or exotic materials," said another US official. The US is now working alongside of Britain combing through evidence. No radical group has claimed responsibility so far. But Islamic state supporters on social media are posting celebratory messages. Victoria train station near the arena was shut down and all people evacuated. British police will be on patrol, some armed some unarmed, the British Transport Police (BTP) said in a statement. This has been the worst attack to hit Britain since July 7, 2005, when a blast killed 52 people in central London.