"Frontier Myanmar's managing editor Danny Fenster today appeared in a special court in Yangon's Insein Prison to face a charge under section 505-A of the Penal Code," the outlet said in a statement.

Fenster was remanded in the prison after the hearing, it said, adding he was scheduled to appear in court again on July 1.

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

Fenster was detained on May 24 at the international airport in Yangon, Myanmar's biggest 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."

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

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

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

Journalist and US citizen Nathan Maung -- who was detained by the junta in March and also faced charges under 505-A -- was released on Monday after the charges were dropped, and has left the country for the US.

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.

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