YANGON: About 100 Myanmar journalists gathered signatures on Friday for a petition denouncing the recent arrests of four reporters that raised concern about the freedom of the media despite a transition from full military rule.

Over a year since Aung San Suu Kyi's National League for Democracy came to power, Myanmar reporters say charges filed by the military this week against journalists reporting on an insurgent group threatened to reverse gains in press freedom.

Suu Kyi has not commented on the reporters, and her spokesman only said journalists must follow the law.

Journalists gathered in the downtown of Yangon, Myanmar's commercial capital, despite pouring rain on Friday afternoon, holding banners saying "stop killing press" and calling for authorities to free the four men immediately.

“Now they are pressuring the media. It's not at the stage of threatening anymore but at the stage of pressuring,” said A Hla Lay Thuzar, co-founder of the Protection Committee for Myanmar Journalists.

Democratic Voice of Burma reporters Aye Nai and Pyae Phone Naing, and Lawi Weng of the Irrawaddy magazine, have been jailed since Monday.

The military accused the three men of breaching a colonial-era Unlawful Associations Act after they covered an event organised by the Ta'ang National Liberation Army, a group seeking autonomy for the Ta'ang ethnic minority that regularly clashes with government troops.

The journalists are due to appear in a court in Shan State in the north of Myanmar on July 11. They face up to three years in prison.

Another journalist, editor Kyaw Min Swe of the Voice newspaper, is awaiting trial under a Telecommunications Act charge of defamation over a satirical article that made fun of the military.

The law's controversial and broadly phrased section 66(d) has been applied to social media users and reporters alike, leading to fears of a chilling effect on free speech.

Aside from the arrests, journalists complain that their access to Kyaw Min Swe's court hearings has been curtailed.

The NLD has a majority in parliament - and many of its lawmakers are former political prisoners - but the party has not prioritised repealing laws that previous governments used to quash dissent.

"Aung San Suu Kyi’s statements about free speech need to be more than just empty promises,” said Paris-based Reporters Without Borders in a statement late on Thursday, calling for the three reporters charged this week to be released.

Human Rights Watch also urged the Myanmar authorities to drop the charges, calling the arrests "a serious blow to media freedom".

At Friday's demonstration, Aung Myo Min, chairman of non-governmental organisation Equality Myanmar, said the recent arrests were a "warning sign for the entire media" in Myanmar.

“I think this is threatening and alarming for all journalists as it shows they can arrest them whenever they want," he said.