“They need to stop,” Beatrice Fihn, the executive director of the International Campaign to Abolish Nuclear Weapons (ICAN) told reporters Friday.
“Nuclear weapons are illegal. Threatening to use nuclear weapons is illegal. Having nuclear weapons, possessing nuclear weapons, developing nuclear weapons, is illegal, and they need to stop.”
The leaders of the United States and North Korea have been in the midst of an escalating war of words; Trump has threatened to rain “fire and fury” on the country; while Kim Jong-un has called Trump a “dotard.”
In a statement, ICAN officials condemned that type of “fiery rhetoric” that could inflame and incite use of nuclear weapons.
“This is a time of great global tension, when fiery rhetoric could all too easily lead us, inexorably, to unspeakable horror. The spectre of nuclear conflict looms large once more. If ever there were a moment for nations to declare their unequivocal opposition to nuclear weapons, that moment is now.”
In her speech announcing the prize, Berit Reiss-Andersen, the leader of the Norwegian Nobel Committee, said the risk that nuclear weapons might be used was now “greater than it has been for a long time.”
ICAN “has been a driving force in prevailing upon the world’s nations to pledge to cooperate … in efforts to stigmatize, prohibit and eliminate nuclear weapons,” Norwegian Nobel Committee chairwoman Reiss-Andersen said in the announcement.
WATCH: White House: Trump against ‘talk’ but not ‘diplomacy’ on North Korea
Fihn said there are no “right hands” for nuclear weapons and stressed that many people are worried about the fact that Trump has access to the nuclear code.
“I think that the election of President Donald Trump has made a lot of people very uncomfortable with the fact that he alone can authorize the use of nuclear weapons.”
It’s not the first time Fihn has been critical of Trump, just two days before being named for the prize, she tweeted out “Donald Trump is a moron.”
While she said she regrets the tweet now, it was in reference to reports that the U.S. Secretary of State Rex Tillerson called Trump a moron. The two have been on opposite sides in recent weeks for how to deal with North Korea; Tillerson has called for diplomacy while Trump has said the time for talks has past.
WATCH: Questions swirl about Rex Tillerson’s relationship with Trump, other administration officials
With a file from Reuters and the Associated Press.