The explosive device used in the Manchester terror attack on Monday evening that has so far been responsible for 22 fatalities and dozens of injuries was worryingly sophisticated, according to a U.K.-based security expert. "The type of weapon is disturbing in some ways because a functioning bomb is actually a fairly sophisticated device to make," Raffaello Pantucci, director of International Security Studies at the Royal United Services Institute (RUSI), told CNBC Tuesday. "There are easy bombs and there are harder bombs but it does always require a certain level of technical ability which either requires a certain amount of training or some practice or some sort of technical skills. And that's always quite worrying," he added, noting that many aspiring bombmakers try and fail. Observing the more common trend in recent years for U.K. terror perpetrators to select cars or knives as the weapon of choice, the security expert said the level of sophistication needed to construct this device will have authorities asking whether the operative was a part of a larger operation.

"To build a successful bomb, that actually will detonate at the right moment that you need it to, requires a little bit more effort and skill. To have one that actually works and to such deadly effect is certainly a disturbing feature of this particular attack," Pantucci commented. Analysts from Jane's Terrorism and Insurgency Centre (JTIC) referred to hospital staff in Manchester saying that they were treating people for shrapnel wounds, which, according to the note's authors indicated "the likely use of an improvised explosive device (IED) filled with nails, ball bearings, or other metal." The attack took place within one of the U.K.'s largest cities which is located in the country's north and counts a population of over half a million people. Ian Hopkins, chief constable of the Greater Manchester Police, said Tuesday that police believe the attack was carried out by one man who had an improvised explosive device and who also died in the bombing. TWEET The British Transport Police has also revealed that the explosion occurred in the foyer area of the Manchester Area, which JTIC analysts suggest illustrates the vulnerability of mass gatherings such as Monday evening's concert which had hosted 21,000 attendees and has overtones of other recent tragic attacks. "Though no claim has been made, the attack fits with the targeting patterns of the Islamist militant groups, with concert venues and clubs targeted previously: For instance in the Islamic State's attack on the Bataclan concert hall in Paris, France, on 13 November 2015 which killed 89 people, or the attack on the Pulse nightclub in Orlando, Florida, on 12 June 2016, which killed 49 people," the JTIC note added.

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While it is more common for terror attacks to take place in capital cities in order to maximize the effect of the political message delivered, it is not abnormal for major cities outside of London to be the target of terrorists, according to Pantucci. He flagged a large Irish Republican Army (IRA) bomb attack in the late 1990s in Manchester and foiled al-Qaeda plots both there and in Liverpool as examples, adding that domestic security services have recognized this and spread out their coverage areas.