Danny Fenster, managing editor of the Frontier Myanmar news outlet, appeared in court "to face a charge under section 505-A of the Penal Code", Frontier said in a statement.

He was later remanded to Yangon's Insein Prison, it said, adding he was scheduled to appear again in court on July 1.

"No reason was given for the filing of the charge against him," the statement said.

Myanmar has been in turmoil since the military seized power in a February 1 coup, with near-daily protests and a huge civil disobedience movement.

Fenster was detained on May 24 at the international airport in Yangon, Myanmar's main city, as he tried to board a plane out of the country.

"We know that Danny has done nothing to warrant this 505-A charge," Frontier said Thursday.

"We condemn his detention and demand his immediate and unconditional release."

Fenster appeared in good health during his appearance, according to his lawyer, Frontier editor-in-chief Tom Kean told AFP.

More than 850 civilians have been killed across Myanmar in an ongoing military crackdown, according to a local monitoring group.

The press has been squeezed as the junta tries to tighten control over the flow of information, throttling internet access and revoking the licences of local media outlets.

The junta revised the 505-A law soon after the coup to include spreading "fake news" as a crime.

Journalist and US citizen Nathan Maung, who was detained by the junta in March and faced the same charge as Fenster, was released on Monday after the charges were dropped, and has left for the US.

The US State Department has said it is "deeply concerned" about Fenster, and demanded his release.

Earlier this month a Myanmar journalist working for another outlet was jailed for two years under the same law, which carries a maximum three-year prison sentence.

Japanese reporter Yuki Kitazumi was detained by authorities in Myanmar in April, and held at Insein until he was freed in May.

In the 2021 Reporters Without Borders Press Freedom Index, Myanmar ranked 140 out of 180 countries.

Since the coup, journalists in Myanmar "face systematic arrest campaigns and censorship", the watchdog said.

Junta leader Min Aung Hlaing has justified his power grab by claiming electoral fraud in the November poll won by Aung San Suu Kyi's National League for Democracy party.