An Irish police investigation into the alleged funding of international terrorism involved the FBI, Met police and Interpol, a court has heard.
The revelation came during the trial of Hasan Bal, 25, who is charged with providing funding for a foreign terror group.
Mr Bal was refused bail when he made his second appearance before Waterford District Court on Tuesday.
Police objected to bail because of the seriousness of the offences.
They also said the accused was a flight risk.
Det Sgt Donal Donohoe told the court: "He no longer has a permanent address in this country."
He also said that, as part of the investigation, police made inquiries "through Interpol and other police forces, primarily the London Metropolitan Police and the FBI".
Mr Bal is charged with providing funding for a foreign terrorist group on 2 October 2015, and attempting to collect funding for a foreign terrorist group on 23 October 2015.
Mr Bal's solicitor Ken Cunningham said the accused's mother was willing to stand bail for him and allow him to live in her home.
Mr Bal's mother, Dr Caroline Ward-Fahy, said it was "very shocking" to be in this situation.
Insp Tony Lonergan asked her how she proposed to ensure, if her son was granted bail, that he would comply with his bail conditions.
"Since my son was born, when I tell him to do something, he will do it," she said. "He will do that as his duty to God because his mother is a very important part of his faith."
Judge Kevin Staunton said he had no doubt Dr Ward-Fahy was a genuine witness and a believable person, and said he accepted she was "shocked by the turn of events that has led her here".
He said he was "influenced greatly" by Det Sgt Donohoe's evidence about Mr Bal being a flight risk.
Judge Staunton refused bail and remanded Mr Bal in custody, to appear again in the district court on 9 May.