The trial of three journalists from Finland’s largest newspaper accused of publishing classified defense intelligence will start next month, with proceedings kicking off in the capital Helsinki on Thursday.

Two journalists and a former editor at the daily Helsingin Sanomat are facing possible prison terms in the case related to a December 2017 investigative report about a defense intelligence unit, which prosecutors said disclosed sensitive information.

The report was part of "a series of articles … on plans – which required a constitutional amendment – to give Finland’s security services greater powers to carry out surveillance and covert operations domestically and abroad," according to the International Press Institute.

As preliminary proceedings commenced at a court in Helsinki, the hearing has been scheduled to begin on Sept. 29, according to Finland’s public broadcaster Yle.

Laura Halminen and Tuomo Pietilainen, who penned the report, and Kalle Silfverberg, former head of the paper’s political news department, were officially charged with disclosing and attempting to disclose state secrets in October 2021.

All three have denied any wrongdoing, with defense lawyers arguing that the published information was already accessible in public sources, according to the Yle report.

Prosecutors contend the journalists were aware of possible criminal liability before publishing the story, and are seeking a "conditional prison sentence" of at least 18 months for each of the defendants, the report said.

The trio could be jailed for between four months and four years, according to Yle.

Helsingin Sanomat’s Editor-in-Chief Kaius Niemi and Managing Editor Esa Makinen were also initially accused in the case, but charges against them were later dropped.