Boston, Massachusetts - The US airman who admitted to leaking a trove of classified Pentagon documents was jailed for 15 years on Tuesday, US media reported.

Jack Teixeira orchestrated the most damaging leak of US classified information in a decade while serving as a junior Massachusetts Air National Guard IT specialist.

He posted highly sensitive documents on the social media platform Discord, from which they spread across the internet.

"I wanted to say that I'm sorry for all of the harm that I've brought and that I've caused, and that I don't think I can really sum up how contrite I am," Teixeira told the court ahead of sentencing, The Boston Globe reported.

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Teixeira, whose family members were in court for the sentencing, was arrested in April 2023 and pleaded guilty in March this year to six federal counts of willful retention and transmission of national defense information.

Because he was on active duty at the time of the offenses, he was subject to both federal law and the Uniform Code of Military Justice.

He will now face a military trial.

The documents leaked by Teixeira pointed to US concern over Ukraine's military capacity against invading Russian forces.

They also showed Washington had apparently spied on allies Israel and South Korea, among other sensitive details.

It was the biggest such breach since the 2013 dump of National Security Agency documents by Edward Snowden, and raised serious questions about access by Teixeira and other junior staffers to high-level secrets.