"Frontier Myanmar is deeply disappointed at the decision today to convict its Managing Editor, Danny Fenster, on three charges and impose prison sentences totalling 11 years," the outlet said in a statement.

Fenster, who was arrested as he tried to leave the country in May, also faces charges of sedition and terrorism, which could see him jailed for life.

The 37-year-old had been working for Frontier Myanmar for around a year and was heading home to see his family when he was detained.

He was later charged with inciting disaffection against the military, breaching visa rules, and unlawful association, and was sentenced at a closed-door trial in Yangon's Insein prison.

"Everyone at Frontier is disappointed and frustrated at this decision," Frontier Myanmar said.

"We just want to see Danny released as soon as possible so he can go home to his family."

Crisis Group Myanmar senior advisor Richard Horsey described the sentence as "outrageous".

"It sends a message not only to international journalists... but also Myanmar journalists that reporting factually on the situation is liable to get them many many years in prison," he told AFP.

Myanmar has been mired in chaos since a February coup, with the military trying to crush widespread democracy protests and stamp out dissent.

More than 1,200 people have been killed by security forces, according to a local monitoring group.

The press has also 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.