Rachid Redouane, center, with the two other London Bridge terrorists
Dr Umar Al Qadri, Imam at the Islamic Centre of Ireland, said it is “very easy” for individuals to slip through the net because they can cross the Irish land border between Northern Ireland and the Republic of Ireland.
The cleric suggested the lack of passport controls in Northern Ireland's capital, Belfast, also made it easy for the individuals to travel.
London terror raids Sun, June 4, 2017
Police have raided a block of flats in Barking in connection with last night's London Bridge terror attack.
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As police continue their investigations following the June 3 terror attacks, a block of flats in Barking is raided for possible suspects
Anyone from Britain can very easily travel to Ireland under the radar
Dr Umar Al Qadri, Imam at the Islamic Centre of Ireland
The attacker Rachid Redouane is thought to have been identified from a card that was found on his body, issued by the Garda National Immigration Bureau in Dublin, according to reports.
The 30-year-old had been refused asylum in the UK so he moved to Ireland, married a British woman there and applied for an EU card, Sky News reports.
Irish authorities are reportedly investigating whether he used the arrangement as an effective back door into the UK.
Redouane's body was reportedly found with an Irish identity card
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Dr Umar Al Qadri, recently warned that people are trying to spread hate online
Dr Umar told Sky News: “Anyone from Britain can very easily travel to Ireland under the radar by travelling to Belfast and at Belfast airports as well as the port, there is no passport controls.
"These individuals can then just take the bus and go to Dublin so it's very easy for them to come to Dublin, come to Ireland and then stay under the radar."
Irish officers have a small number of people on their terrorist watch-list, but Redouane was not among them, reports have claimed.
Tom Clonan, a retired Army Captain, said the lack of capability poses a serious threat in the current security climate.
He said: "Islamic State are attracted by weakness and gaps in security and Ireland is Europe's weakest link in terms of our defence, intelligence and policing infrastructure unfortunately so it's very porous between here and the UK.”
A view of Grosvenor Square, Rathmines where terrorist Rachid Redouane used to live
The news comes as the Australian government confirmed two of their country’s citizens were killed in Saturday night’s terror attack.
One of the victims was identified as Kirsty Boden, a 28-year-old nurse from South Australia, who was confirmed dead on Tuesday, but the other victim has not yet been named.