The Geneva-based ICAN won the $1.1 million prize because it "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 Berit Reiss-Andersen said in the announcement.
The prize "sends a message to all nuclear-armed states and all states that continue to rely on nuclear weapons for security that it is unacceptable behavior. We will not support it, we will not make excuses for it, we can't threaten to indiscriminately slaughter hundreds of thousands of civilians in the name of security. That's not how you build security," ICAN executive director Beatrice Fihn told reporters in Geneva.
She said that she "worried that it was a prank" after getting a phone call just minutes before the official Peace Prize announcement was made. Fihn said she didn't believe it until she heard the name of the group proclaimed on television.
"We are trying to send very strong signals to all states with nuclear arms, nuclear-armed states - North Korea, U.S., Russia, China, France, U.K., Israel, all of them, India, Pakistan - it is unacceptable to threaten to kill civilians," she said.
The prize comes amid heightened tensions over both North Korea's aggressive development of nuclear weapons and President Donald Trump's persistent criticism of the deal to curb Iran's nuclear program.
"The panel wants to send a signal to North Korea and the US that they need to go into negotiations. The prize is also coded support to the Iran nuclear deal. I think this was wise because recognizing the Iran deal itself could have been seen as giving support to the Iranian state," Oeivind Stenersen, a historian of the peace prize, told The Associated Press.
Reiss-Andersen noted that similar prohibitions have been reached on chemical and biological weapons, land mines and cluster munitions.
"Nuclear weapons are even more destructive, but have not yet been made the object of a similar international legal prohibition," she said.
Reiss-Andersen said "through its inspiring and innovative support for the U.N. negotiations on a treaty banning nuclear weapons, ICAN has played a major part in bringing about what in our day and age is equivalent to an international peace congress."
Asked by journalists whether the prize was essentially symbolic, given that no international measures against nuclear weapons have been reached, Reiss-Andersen said "What will not have an impact is being passive."
Jamey Keaten in Geneva and Jim Heintz in Stockholm contributed to this story.
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