This artist’s depiction shows Massachusetts Air National Guard member Jack Teixeira, right, appearing in U.S. District Court in Boston in April 14. Teixeira has pleaded not guilty to willful retention and transmission of national defense information. Margaret Small via Associated Press

WORCESTER, Mass. — Jack Teixeira, the Massachusetts Air National Guard member accused of leaking highly classified military documents on a social media platform, pleaded not guilty Wednesday to federal felony charges.

Teixeira, 21, entered the pleas during a hearing in Worcester’s federal court days after he was indicted by a grand jury on six counts of willful retention and transmission of national defense information. Each count is punishable by up to 10 years in prison.

Handcuffed and wearing orange jail garb, Teixeira smiled at family seated in the gallery at the start of the hearing. He stood at the defense table next to his lawyers and leaned over to say “not guilty, your honor” into the microphone after the judge read each count. The judge also denied a defense request to reconsider his detention order.

Teixeira, of North Dighton, has been behind bars since his April arrest on charges stemming from the most consequential intelligence leak in years. A magistrate judge ruled last month that Teixeira must remain in jail while the case plays out, saying that releasing him would pose a risk that he would attempt to flee the country or obstruct justice.

The leak left the Biden administration scrambling to assess and contain the damage among the international community and reassure allies that its secrets are safe with the U.S.

Teixeira’s attorney has said his client “will answer the charges” and “will be judged by his fellow citizens.” In pushing for his release, Teixeira’s attorneys argued that the government isn’t alleging Teixeira ever intended that the information be widely disseminated.

Teixeira’s family said in an emailed statement last month that they “remain committed as ever” to supporting him.

Teixeira is accused of sharing classified military documents about Russia’s war in Ukraine and other sensitive national security topics on Discord, a social media platform popular with people playing online games. Investigators believe he was the leader of an private chat group called Thug Shaker Central, where enthusiasts shared jokes, talked about their favorite types of guns and discussed wars, including Russia’s invasion of Ukraine.

Authorities say Teixeira, who enlisted in the Air National Guard in 2019, began around January sharing military secrets with other Discord users — first by typing out classified documents and then sharing photographs of files that bore SECRET and TOP SECRET markings. Teixeira worked as a a “cyber transport systems specialist,” essentially an IT specialist responsible for military communications networks.

Prosecutors say he continued to leak government secrets even after he was warned by superiors about mishandling and improper viewing of classified information. After being admonished by superiors last year, he was again seen in February viewing information not related to the intelligence field, not his primary duty, according to internal Air National Guard memos filed in court.

Justice Department lawyers revealed in earlier court filings that Teixeira had a history of disturbing online remarks. He wrote in November that he would “kill a (expletive) ton of people” if he had his way, because it would be “culling the weak minded.” He also used his government computer in July to look up mass shootings, searching terms such as “Mandalay Bay shooting” and “Uvalde,” prosecutors said.

Authorities have provided few details about an alleged possible motive, but accounts of those in the online private chat group where the documents were disclosed have depicted Teixeira as motivated more by bravado than ideology.

Attorney General Merrick Garland said in a statement last week that Teixeira was entrusted with information “that reasonably could be expected to cause exceptionally grave damage to national security if shared.”