STORY: "Our blood is boiling today," Aung Naing Soe, a self-exiled journalist from Myanmar, told Reuters.
Sentenced to death in closed-door trials in January and April, the men had been accused of helping a resistance movement to fight the army that seized power in a coup last year and unleashed a bloody crackdown on its opponents.
Despite the international calls for the junta to end prosecutions against activists, the move to execute them was deemed as a 'slap in the face' for the international community.
"I think that the junta's trying to make a chilling environment for activists, for pro-democracy activists, for human rights defenders inside Myanmar. But this won't stop the revolution," said Patrick Phongsathorn, Human Rights Advocacy Associate of Fortify Rights. "They will be more determined than ever to remove this brutal regime."
Meanwhile, deputy Asia director for Human Rights Watch Phil Robertson voiced concerns there could be more pro-democracy activists on death row.
"Now that the dam has broken and they've killed these four political prisoners that they will continue with others," he told Reuters.
The junta spokesman last month defended the death penalty, saying it was justified and used in many countries.
Myanmar's National Unity Government (NUG), a shadow administration outlawed by the ruling junta, condemned the executions and called for international action against the ruling military.