One of the London Bridge terrorists was carrying an identity card issued in Ireland when he was shot dead, security sources in Dublin said.
The revelation comes after reports one of the three men had also appeared in a Channel 4 documentary about jihadis in the UK.
The 27-year-old, said to be from Barking in east London, was pictured lying on the ground after police arrived on Saturday night and shot the attackers dead.
Seven people were killed and 49 injured when the trio drove a van into pedestrians on London Bridge before stabbing people in bars in nearby Borough Market.
Irish broadcaster RTE reported authorities found an Irish identity card on the body of one of the suspects, indicating he had previously lived in Ireland.
Police chiefs in Dublin said they were working with counterparts in the UK.
“An Garda Siochana is providing every assistance to our colleagues in the London Metropolitan Police in relation to the terror attack in London,” a spokesman said.
“We will process all requests from the UK authorities in relation to inquiries into individuals, identities or any other matter.”
There are unconfirmed reports the man who had been carrying the Irish-issued ID may have claimed to be from Morocco, and that he was married to a woman from Scotland and had lived in Dublin.
Gardai are investigating whether the ID card belonged to the dead man and if the documents are legitimate.
It is understood inquiries are continuing into whether the man was given an Irish ID card issued by the Garda National Immigration Bureau.
The plastic credit card-sized documentation is given to people from outside the EU. It has a person's certificate of registration which states they have permission to stay in Ireland and must be carried at all times.
There are also inquiries into whether the man had been given paperwork after landing in Ireland to claim asylum or if he had an ID card issued under EU treaties which allowed him to live in Ireland with his family.
Garda Commissioner Noirin O'Sullivan was holding a meeting with the force's anti-terror and intelligence chiefs as they co-operate with the Met investigation.
Additional reporting by agencies
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