On Wednesday, two Reuters reporters will have spent one year in a Myanmar prison, where they are serving seven-year sentences for reporting on a military massacre of Rohingya Muslims.

Rights groups say the prolonged detention of the two journalists is a blemish on the record of the nominally democratic government headed by State Counsellor Aung San Suu Kyi.

Wa Lone, 32, and Kyaw Soe Oo, 28, were arrested in Yangon on December 12, 2017, while reporting on the killing of 10 Rohingya men and boys in the village of Inn Din the previous September.

The massacre is one of several that have been documented by UN investigators, who say that the military's so-called counterinsurgency operations against Rohingya communities in northern Rakhine state starting in August 2017 were carried out with "genocidal intent."

A police officer who was involved in the Inn Din massacre testified during the reporters' trial that their arrest was a trap set by a senior police official with the aim of suppressing their reporting.

The reporters themselves have testified that police tried to persuade them to withhold their reporting in exchange for their freedom.

In February, Reuters published a detailed account of the massacre, and in April, a military tribunal sentenced seven soldiers to 10 years in prison for murder.

But despite the military's admission of guilt, Wa Lone and Kyaw Soe Oo were convicted in September on charges of possessing secret government information in violation of the Official Secrets Act.

Their sentencing has signalled to Myanmar journalists and free speech advocates that exposing the military's abuses, no matter how accurate, is considered a criminal act.

"Self-censorship has increased because Myanmar journalists have learnt that it does not matter how professional you are, how well regarded your media is, or how important your story may be," said Yin Yadanar Thein, director of Free Expression Myanmar (FEM), an organization that monitors laws used to suppress political dissent.

"If you talk or write about the military, you will go to prison for a long, long time," she added.

Shortly before Wa Lone and Kyaw Soe Oo were arrested, FEM published a report showing that defamation cases had skyrocketed after the National League for Democracy (NLD), the party headed by Suu Kyi, came to power.

Although the government she now leads is constrained by the military, which retains control over key organs of the state, including the police, many have pointed out that she has abetted the military's blockade on criticism.

"Aung San Suu Kyi seems to have decided that it is better to cover up problems than to admit her powerlessness to solve them. As a result, her government has actively increased propaganda while undermining media freedom," said Yin Yadanar Thein.

Access to northern Rakhine state remains heavily restricted, and a government agency headed by Suu Kyi has been bulldozing villages vacated by the 700,000 Rohingya who were driven from the country during last year's military operations, destroying what rights groups consider to be crime scenes.

Reuters said the fact that its journalists were still in prison "for a crime they did not commit" called into question "Myanmar’s commitment to democracy, freedom of expression and rule of law."

"Every day they continue to be behind bars is a missed opportunity for Myanmar to stand up for justice,” a spokesman for the news agency said.

Lawyers for Wa Lone and Kyaw Soe Oo say they plan to continue fighting for their clients' freedom. They are scheduled to present their arguments in an appeal to a higher court on December 24.

"We will focus on the unjust manner of the original trial," defence lawyer Than Zaw Aung, who represented the two reporters in their first trial and who is also handling their appeal, told dpa.

"The first trial was controversial because of [its relevance to] freedom of expression, the right to information, and the government's attitude. There was a lot of pressure from inside and outside, so the judge may have decided on the case [based on that pressure]," the lawyer said.

He said he expects a verdict on the appeal to be passed down within two months of the hearing.

Than Zaw Aung stressed that his clients are innocent and carried out their duties in accordance with journalistic ethics, and he encouraged other journalists in the country not to be discouraged from reporting on the military.

"Journalists are the fourth estate," said Than Zaw Aung. "They are trying to get the right information for the people, so they should continue their work."