Journalists in Myanmar believe their government is failing to defend media freedom despite the transition from harsh military rule to an elected government of Aung San Suu Kyi, according to a survey published to mark World Press Freedom Day on Thursday.

Activist group Free Expression Myanmar and its partner organizations interviewed 200 journalists between January and April, finding almost half believed they had less freedom as journalists than a year earlier.

"Journalists are frustrated by the government's failure to implement its election manifesto commitments to increase media freedom," the group said in a report on its survey.

Asked to rate the government's success on defending media freedom, 79 percent of journalists questioned for the survey answered "low" or "very low."

The government's main spokesman, Zaw Htay, referred Reuters' questions about the survey results to the information ministry.

Reuters contacted three officials at the Ministry of Information, who all declined to comment and referred questions to other officials.

The military ruled Myanmar for nearly 50 years but handed over the reins of government to Nobel laureate Suu Kyi in early 2016. The military retains control of government ministries responsible for security, including interior and defence.

Police arrested two Reuters reporters on Dec. 12 and they face up to 14 years in prison under accusations they breached the colonial-era Official Secrets Act.

The survey comes after Paris-based Reporters Without Borders last week moved Myanmar down in its annual press freedom index by six places to 137th out of 180 nations, citing legal action against journalists and restrictions on access to conflict-affected areas.

"Journalists increasingly believe that the government, including the military, is the greatest threat to media freedom in Myanmar, both through its continued use of old oppressive laws which it has no real plans to amend and its adoption of new oppressive laws," the group said in its report.

Several journalists have faced legal action in connection with their work over the past year or more, but according to Advocacy group Athan, or "voice", the two Reuters journalists - Wa Lone, 32, and Kyaw Soe Oo, 28 - are the only reporters in detention.

Several US lawmakers expressed solidarity with Wa Lone and Kyaw Soe Oo, and other imprisoned journalists, to mark World Press Freedom Day. Nine US senators signed a letter to the two men promising to continue to urge the country's authorities to release them and drop all charges.

A court is holding hearings to decide whether the two Reuters journalists will face trial for allegedly handling secret government documents.

At the time of their arrest, the reporters had been working on an investigation into the killing of 10 Rohingya Muslim men and boys in a village in western Myanmar’s Rakhine State.

The killings took place during an army crackdown that United Nations agencies say sent nearly 700,000 people fleeing to Bangladesh.

"Press Freedom Day is very meaningful for us," Wa Lone told reporters on the steps of a Yangon court on Wednesday, following the most recent hearing.

"We know how important it is because we spend every day in prison."