The four people arrested by gardaí earlier this week on suspicion of financing terrorist activities have been released.

On Tuesday morning members of the Special Detective Unit, the Garda National Economic Crime Bureau and Security and Intelligence unit raided six properties in Dublin as part of an investigation into the funding of terrorism.

Detectives seized documents, electronics and €4,500 worth of cash. A man in his 40s and three women, aged between 30 and 70, were arrested under Section 13 of the Criminal Justice (Terrorist Offences) Act, 2005.

Gardaí said on Wednesday while the four had been released their investigations are ongoing a file will be prepared for the Director of Pubic Prosecutions.

Gardaí believe a group of Dublin-based Isis fundraisers was collecting money in the Republic and sending it to the terrorist group in Syria while staying below the radar of international security services..

Gardaí believe at least tens of thousands of euros was sent to Isis in Syria.

The four who were detained included a man, his sister, his partner and former partner.

The Garda has had suspected Islamic State, or Isis, sympathisers, fundraisers, recruiters and foreign fighters on a watch list for well over a decade.

However, it is understood the four people arrested on Tuesday were not being watched over a long period of time. They came to the attention of the Garda more recently after evidence emerged suggesting money transfers from Dublin had been made to Syria.