The U.S. Department of Justice (DOJ) announced the "largest ever seizure of terrorist organizations' cryptocurrency accounts" on Thursday, including "millions of dollars" and 300 crypto accounts.

In a press release Thursday, the DOJ announced it had investigated and dismantled "three terrorist financing cyber-enabled campaigns" involving al-Qaeda, Hamas and the Islamic State of Iraq and the Levant (ISIS).

Legal documents filed Thursday show the DOJ is trying to seize bitcoin from 155 addresses it alleges were used by Al Qaeda to fund terrorism and arrest two individuals allegedly involved with facilitating crypto transfers for Hamas.

In a complaint for forfeiture, the FBI, Homeland Security Investigations (HSI) and Internal Revenue Service cyber-crimes unit claim that Al Qaeda created a sophisticated money-laundering operation through a network of Telegram channels, which they used to solicit bitcoin donations intended to fund acts of terror.

"Al-Qaeda and affiliated terrorist groups have been operating a BTC money laundering network using Telegram channels and other social media platforms to solicit BTC donations to further their terrorist goals," the complaint read. "As described below, al-Qaeda and affiliated terrorist groups operate a number of Telegram channels and purport to act as charities when, in fact, they are soliciting funds for the mujahadeen."

The complaint starts with donations sent to a Telegram group called "Tawheed & Jihad Media," which began soliciting bitcoin donations in April 2019.

Overall, the investigators found 155 different crypto addresses they claim are tied to Al Qaeda and various other organizations allegedly supporting the terrorist group.

Funds were sent to gift card exchanges and other platforms, according to the filing.

"The Defendant Properties are subject to forfeiture to the United States ... as assets of a foreign terrorist organization engaged in planning or perpetrating any federal crime of terrorism," the complaint said.

A separate affidavit in support of an arrest warrant detailed how Mehmet Akti and Hüsamettı̇n Karataş allegedly stored and transferred cryptocurrencies, including bitcoin, ether, XRP and EOS on behalf of al-Qassam, Hamas' military wing.

The affidavit alleges the two violated money services business regulations and the Bank Secrecy Act.

Investigators used Chainalysis and Excygent to track bitcoin transfers from these organizations over the last 18 months.

In a blog post, Chainalysis said authorities seized more than $1 million from terror campaigns. The blog post went on to describe how the company tracked the funds, noting that many of the addresses "are hosted at various exchanges."

According to the Middle East Media Research Institute, Telegram groups were soliciting bitcoin for terrorist groups as recently as July 2020.

Leigh Cuen contributed reporting.

Read the full complaint below:

UPDATE (Aug. 13, 2020, 16:55 UTC): This article has been updated with additional information.