Four people, including former MP Phyo Zeya Thaw and democracy activist Ko Jimmy, "who were sentenced to death will be hanged according to prison procedures", junta spokesman Zaw Min Tun told AFP.

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 lawmaker from 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.

"They continued the legal process of appealing and sending a request letter for the amendment of the sentence," the spokesman said.

"But the court rejected their appeal and request. There is no other step after that," he added.

Two other men, who were convicted and sentenced to death for killing a woman they alleged was an informer for the junta in Yangon, will also be executed, the spokesman said.

No date has been set for the executions, Zaw Min Tun said.

United Nations Secretary-General Antonio Guterres condemned the junta's decision, calling it "a blatant violation to the right to life, liberty and security of person", according to his spokesman Stephane Dujarric.

Guterres called for the two pro-democracy activists to be released and all the charges against them to be dropped.

"The Secretary-General considers that the death penalty cannot be reconciled with full respect for the right to life," Dujarric told reporters.

"Abolition is necessary and desirable for the enhancement of human dignity and the progressive development of human rights."

A spokesperson for Amnesty International called on the junta to "immediately drop such plans and for the international community to step up its efforts to intervene".

- 'Fuel to the fire' -

The junta's decision to "move towards executing two prominent political leaders will be like pouring gasoline on the fire of popular anti-military resistance in the country", said Phil Robertson, a deputy director at Human Rights Watch.

"Such a move will also lead to global condemnation and cement the junta's reputation as among the worst of the worst human rights abusers in Asia."

Phyo Zeya Thaw had been accused of orchestrating several attacks on regime forces, including a gun attack on a commuter train in Yangon in August that killed five policemen.

A hip-hop pioneer whose subversive rhymes irked the previous junta, he was jailed in 2008 for membership of an illegal organisation and possession of foreign currency.

He was elected to parliament representing Aung San Suu Kyi's NLD in the 2015 elections, which ushered in a transition to civilian rule.

The country's military alleged voter fraud during elections in 2020 -- which the NLD won by a landslide -- as justification for its coup on February 1 last year.

Suu Kyi has been detained ever since and faces a slew of charges in a junta court that could see her face a prison sentence of more than 150 years.

Kyaw Min Yu, who rose to prominence during Myanmar's 1988 student uprising against the country's previous military regime, was arrested in an overnight raid in October.

The junta issued an arrest warrant for him last year, alleging he had incited unrest with his social media posts.