Jack Teixeira, a US Air National Guardsman who leaked Pentagon documents last year in one of the highest-profile intelligence cases in recent years, has been sentenced to 15 years in prison.

Teixeira, 22, pleaded guilty to the wilful retention and transmission of national defence information in March.

While he worked at an Air National Guard base, Teixeira obtained materials including maps, satellite images and intelligence on US allies, and then posted those documents to an online platform popular with gamers.

Among the documents he shared was confidential information about the war in Ukraine.

Prosecutors asked US District Court Judge Indira Talwani to impose a 16 and a half-year sentence on Teixeira. His defence lawyers asked for an 11-year sentence.

In their request for a lenient sentence, Teixeira's lawyers argued in court filings that the airman was the target of bullying while in high school and his military unit, and that he had suffered from isolation.

Meanwhile, prosecutors argued for a longer prison term, saying that the airman had "perpetrated one of the most significant and consequential violations of the Espionage Act in American history".

"Teixeira understood the risk to his country and did it anyways," prosecutors told Judge Talwani on Tuesday.

Passing sentence, Judge Talwani said to Teixeira: "You are young and you have a future ahead of you, but it is such a serious crime."

Teixeira apologised before the court, and said he understood that "all the responsibility and consequences fall on my shoulders alone", according to reporters inside the Boston court.

Teixeira began with a small group of gun and military enthusiasts on a Discord server, or chatroom, in late 2022. While the documents stayed in that chatroom initially, the information was later re-shared on more public channels.

The documents were later picked up by pro-Kremlin Telegram channels and military bloggers.

Teixeira enlisted in the Massachusetts Air National Guard, a reserve of the US Air Force, in 2019. In that role, he had top-secret security clearance.

In order to get this clearance, Teixeira signed a "lifetime binding non-disclosure agreement" acknowledging that the "unauthorized disclosure of protected information could result in criminal charges", according to court documents.

Teixeira's leak prompted the Pentagon to examine its systems for handling classified information.