Myanmar: Decades later, the death penalty is being used again in Myanmar. Military goverment leader junta will execute a former member of Aung San Suu Kyi's party, Phyo Zeya Thaw and democracy activist Ko Jimmy, both of whom were convicted of terrorism.

The junta has sentenced dozens of anti-coup activists to death as part of its crackdown on dissent after seizing power last year, but Myanmar has not carried out an execution for decades.

Phyo Zeya Thaw, a former member of Aung San Suu Kyi's National League for Democracy who was arrested in November, was sentenced to death in January for offences under anti-terrorism laws.

Prominent democracy activist Kyaw Min Yu — better known as "Jimmy" — received the same sentence from the military tribunal.

The United Nations said it was "deeply troubled" by Friday's announcement, which UN spokesman Stephane Dujarric described as a blatant human rights violation.

UN Secretary-General Antonio Guterres called for charges to be dropped "against those arrested on charges related to the exercise of their fundamental freedoms and rights and for the immediate release of all political prisoners in Myanmar," Mr Dujarric said.

It was unclear whether Kyaw Min Yu and Phyo Zayar Thaw had denied the charges against them. The junta statement did not mention their pleas.

Their appeals against the sentences were rejected, a junta spokesperson said, though it was unclear by whom. The activists' representatives could not be reached for comment.

"Previously, the convicts sentenced to death could appeal and if no decision was made, then their death sentences would not be implemented," junta spokesperson Zaw Min Tun told.

"At this time, that appeal was rejected so the death sentences are going to be implemented," he said.

He did not say when the executions would take place.

Judges in Myanmar sentence offenders to death for serious crimes including murder, but no one has been executed in decades.

The last judicial execution to be carried out in Myanmar is generally believed to have been of another political offender, student leader Salai Tin Maung Oo, in 1976 under a previous military government led by dictator Ne Win.