Jack Teixeira was arrested Thursday following a week-long probe into one of the most damaging leaks of secrets since the 2013 dump of National Security Agency documents by Edward Snowden.

He was charged with the "unauthorized retention and transmission of national defense information" at a short hearing in Boston.

He is also accused of the "unauthorized removal and retention of classified documents or material."

The embarrassing security breach has revealed American concerns about weaknesses in Ukraine's military, and pointed to US spying on allies including Israel and South Korea.

Teixeira appeared before a judge at Massachusetts federal court in Boston at 10:00 am (1400 GMT).

He was not required to enter a plea and was detained pending a detention hearing set for next Wednesday.

He is suspected of posting the documents, some dated as recently as early March, to a private chat group on the social media platform Discord.

The New York Times reported that Teixeira was the leader of the group called Thug Shaker Central and reportedly posted the documents under the nickname "OG".

He first wrote down the contents of classified documents to share with the group, but later began taking photos, telling other members not to share them, according to the Washington Post.

Some of the documents later appeared on other sites, including Twitter, 4Chan and Telegram.

- Military family -

Investigators have not yet suggested what Teixeira's motive was.

He enlisted with the US Air Force National Guard in September 2019 and was an IT and communications specialist who reached the rank of airman first class -- the third-lowest for enlisted air force personnel.

The leak has raised questions about why someone in such a junior position had access to such potentially damaging secrets.

Friends of Teixeira described him to the Washington Post as a devout Catholic and libertarian who is interested in guns.

The newspaper reported that he comes from a family with decades of military service. His father spent 34 years in the same military unit as his son while Teixeira's mother worked for non-profit organizations that support veterans.

Teixeira's dramatic arrest at his home in the southern Massachusetts town of North Dighton was broadcast live on US TV networks Thursday.

Helicopter footage of the operation showed the suspect dressed in red shorts and a T-shirt with his hands behind his head, backing slowly toward rifle-armed, camouflage-clad law enforcement personnel who took him into custody.

US Attorney General Merrick Garland told reporters that Teixeira had been arrested "in connection with an investigation into alleged unauthorized removal, retention and transmission of classified national defense information."

US Defense Secretary Lloyd Austin said he was ordering a "review of our intelligence access, accountability and control procedures within the (Defense) Department to inform our efforts to prevent this kind of incident from happening again."