Anti-nuclear Nobel Peace group displays paper birds made by Hiroshima children
The International Campaign to Abolish Nuclear Weapons, the recipient of this year's Nobel Peace Prize, has installed 1,000 red paper cranes outside the Norwegian Parliament before formally receiving the award.
The cranes were made by children in Hiroshima, Japan, site of the world's first atomic bomb attack.
ICAN executive director Beatrice Fihn said at the installation: "Right now we see the threats of using nuclear weapons being increased.
"States are actively making these threats - to kill hundreds of thousands of civilians.
"This is not a joke. This is a real threat that we need to fix and this is fixable. We can fix this."
The prize is to be formally presented on Sunday.
Ms Fihn told a news conference at the Norwegian Nobel Committee that as long as atomic bombs exist, a disaster is inevitable.
"We are facing a clear choice right now: The end of nuclear weapons or the end of us," she said.
"An impulsive tantrum, a calculated military escalation, a terrorist or cyber attack or a complete accident - we will see the use of nuclear weapons unless they are eliminated.
"These weapons do not make us safe, they are not a deterrent, they only spur other states to pursue their own nuclear weapons. And if you are not comfortable with Kim Jong-un having nuclear weapons, then you are not comfortable with nuclear weapons. If you're not comfortable with Donald Trump having nuclear weapons, then you are not comfortable with nuclear weapons."
ICAN, which brings together more than 450 organisations, was a driving force behind an international treaty on banning nuclear weapons that was passed this year.
So far, 53 countries have signed up, but only three have ratified it - the treaty needs ratification by 50 to go into effect.
No nuclear power has signed the treaty. Three major nuclear powers - the United States, Britain and France - have said they will not send their ambassadors to Sunday's Nobel prize ceremony in the Norwegian capital.
Satsuko Thurlow, a survivor of the Hiroshima atomic bombing who is to accept the prize along with Ms Fihn, said she was "not too surprised" at the diplomatic snub.
"This is not the first time they have behaved that way... they tried in many different ways to sabotage, to discredit, what we tried to do," she said. "Maybe this shows they are really annoyed at what success we have had so far."