Messages of solidarity poured in, on Wednesday from around the world on the one-year anniversary of the arrest of two Myanmar Reuters journalists who exposed a massacre of Rohingya Muslims in Rakhine state.

Wa Lone, 32, and Kyaw Soe Oo, 28, were arrested in Yangon on December 12 and handed seven-year jail sentences under a state secrets law as they probed the extrajudicial killing of 10 Rohingya men during the military's brutal crackdown on the stateless minority last year.

The guilty verdict sparked global condemnation, including from US Vice President Mike Pence, and Reuters hired prominent rights attorney Amal Clooney to assist with the case.

The reporters were also honoured alongside other persecuted or slain journalists in Time magazine's Person of the Year issue this week as concerns grow for deteriorating press freedoms in Myanmar and elsewhere in the world.

Despite a tenacious advocacy campaign the two men remain behind bars, with an appeal set for later this month.

"The fact that they remain in prison for a crime they did not commit calls into question Myanmar's commitment to democracy, freedom of expression and rule of law," Reuters editor-in-chief Stephen J. Adler said in a statement on the anniversary of the arrest.

Social media platforms have filled with images of supporters making the "thumbs up" gesture that became a hallmark of the pair's court appearances.

A rally with journalists and activists is due to take place in downtown Yangon on Wednesday afternoon.

"We will face it (the verdict) with stability and courage," Wa Lone said after the sentence was handed down in September.

"The government can detain us in the prison but... don't close the ears and eyes of the people," Kyaw Soe Oo said.

Their personal ordeal has also moved many who have followed the case. Both men are fathers and Wa Lone's wife Pan Ei Mon gave birth to their first child shortly before he was convicted.

One of the Time covers shared widely online features Pan Ei Mon and Kyaw Soe Oo's wife Chit Su Win holding photos of their imprisoned husbands.

The magazine jointly honoured a number of journalists -- including the slain columnist Jamal Khashoggi, Philippine journalist Maria Ressa and the workforce of the US newspaper Capital Gazette, five of whose staff were killed in a June shooting -- "for taking great risks in pursuit of greater truths".

The reporters' trial was widely regarded as a sham -- and punishment for reporting on the September 2017 massacre in Inn Din village led by Myanmar security forces.

One whistleblowing police officer told the court his superior ordered a sting to entrap the reporters -- testimony the judge chose to ignore.

Myanmar's civilian leader Aung San Suu Kyi remained defiant when pressed on the case, insisting that due process was followed.

Her reaction further tarnished her image as a democracy icon overseas after she refused to speak up for the Rohingya during the crackdown.

More than 720,000 Rohingya Muslims fled over the border into refugee camps in Bangladesh, bringing with them horrific reports of widespread murder, torture, rape and arson.

UN investigators have called for top generals to be prosecuted for genocide and accused Suu Kyi and her government of complicity.

Myanmar rejects almost all allegations, saying it was defending itself against Rohingya militants.

But a court did convict soldiers accused of carrying out the Inn Din massacre to 10 years each.