The govt said the California-based Vietnam Reform Party had recruited and trained operatives to use weapons and explosives.
US President Barack Obama on Friday issued an executive order to lift economic sanctions on Myanmar.
The explosion of Mount Aso also blew off bits of volcanic rock and ash.
US military has already been told Philippine President Rodrigo Duterte wants to halt the joint patrols and naval exercises.
Council members are expected to vote on a draft resolution demanding an end to air strikes and military flights over Aleppo.
The UN body condemned the Saudi-led coalition's air strikes in Yemen, which reportedly killed and maimed hundreds of children.
The piece of wing flap was found in May and subsequently analyzed by experts at the Australian Transport Safety Bureau.
It is the latest in a series of allegations against the military government that seized power in May 2014.
Activity was reported at all three tunnel complexes at the Punggye-ri nuclear test site involving a large vehicle and personnel.
The offer of amnesty follows two weeks of the heaviest bombardment of the five-and-a-half-year civil war, which has killed hundreds.