WASHINGTON - U.S. authorities have seized millions of dollars and hundreds of virtual currency accounts used to funnel money to al-Qaida, Islamic State (IS) and Hamas's military wing, the Justice Department announced Thursday.

The department said the seizure of the more than 300 cryptocurrency accounts linked to the three groups was the largest of its kind and amounts to a disruption of their ever-changing fundraising methods.

"It should not surprise anyone that our enemies use modern technology, social media platforms and cryptocurrency to facilitate their evil and violent agendas," Attorney General William P. Barr said in a statement. "The Department of Justice will employ all available resources to protect the lives and safety of the American public from terrorist groups."

The seized accounts belonged to the three terror groups, their unidentified donors and "money transmitters" operating on virtual currency exchanges around the world, according to court documents. More than 150 of the accounts were used in fundraising carried out by the al-Qassam Brigades, Hamas's military wing.

Two Turkish money transmitters - Mehmet Akti and Husamettin Karataş - were charged with helping Hamas "cash out" the bitcoin donations while operating an unlicensed money transmitting business. Akti served hundreds of customers, including six who lived in the U.S. or used U.S. based accounts, according to court documents.

"While these individuals believe they operate anonymously in the digital space, we have the skill and resolve to find, fix and prosecute these actors under the full extent of the law," said Acting United States Attorney for the District of Columbia Michael R. Sherwin.

Bitcoin is a virtual currency. Although all bitcoin transactions are posted to a public ledger known as Blockchain, its users are not identified, making it a "pseudo-anonymous" currency.

Experts and policymakers have long raised concern that terrorist groups will exploit this anonymity to fund their activities. In recent years, IS and the al-Qassam Brigades have been known to use bitcoin. According to a 2019 RAND Corporation report, terrorist organizations use cryptocurrencies for a wide range of activities, from fundraising to drug and arms trafficking and operational funding.

Social media involved

The al-Qassam Brigades's digital currency fundraising began in early 2019 with a call on Twitter to "Donate to Palestinian Resistance via Bitcoin," according to court documents. The group then moved its plea to its official websites, telling followers that bitcoin donations were "untraceable" and "would be used for violent causes."

"Their websites offered video instruction on how to anonymously make donations, in part by using unique bitcoin addresses generated for each individual donor," the Justice Department said in a statement.

Uncovering the donations, including donations made by people based in the U.S., agents from the FBI, IRS, and Homeland Security Investigations (HSI) tracked and seized more than 150 accounts that had funneled money into al-Qassam Brigades accounts.

"As demonstrated by this recent operation, the FBI remains committed to cutting off the financial lifeblood of these organizations that seek to harm Americans at home and abroad," FBI Director Christopher Wray said.

In IS's case, the Justice Department seized a fake face mask seller website and Facebook pages belonging to Murat Cakar, a Turkish IS facilitator allegedly responsible for the group's hacking operations.