A portrait photo of Japanese documentary filmmaker Toru Kubota is displayed during a news conference at the Japan National Press Club in Tokyo.
CNN  — 

A military court in Myanmar has sentenced a Japanese journalist to 10 years in prison for sedition and violating a law on electronic communications after he filmed an anti-government protest in July, a Japanese diplomat said on Thursday.

Toru Kubota, 26, was arrested by plainclothes police in Yangon, where he was filming a documentary that he had been working on for several years, according to a Change.org petition calling for his release.

Kubota was sentenced on Wednesday to three years for sedition and seven years for the communications charges, according to Tetsuo Kitada, the deputy chief of mission at the Embassy of Japan in Myanmar, citing a lawyer representing the filmmaker’s case.

Kitada told CNN the court ruling had been made “behind closed doors,” and that Kubota’s lawyer was not allowed to be present.

Closed-door trials with no access for media or the public have become the norm in Myanmar, with rights groups and observers saying such trials violate international human rights.

The Japanese embassy is “doing its best” to secure an early release for Kubota, Kitada added.

Freedoms and rights in Myanmar under the military junta continue to deteriorate, rights groups and observers say. State executions have returned and the number of documented violent attacks by the army on civilian areas, including schools, has surged, according to non-governmental organizations.

Its deposed former leader Aung San Suu Kyi remains imprisoned with mounting charges made against her by the ruling junta. She has denied all allegations made against her and her supporters say the charges are politically motivated.

Kubota joins other foreigners being held in prison in Myanmar.

Australian Sean Turnell, a former economic advisor to Suu Kyi and her party, was sentenced to three years in prison for violating the country’s Official State Secrets Act – a ruling immediately rejected by the Australian government.

Vicky Bowman, the United Kingdom’s former ambassador to Myanmar who served as its top diplomat in Myanmar between 2002 and 2006, was charged with immigration offenses along with her husband and sent to Yangon’s notorious Insein Prison.