The group's executive director, Beatrice Fihn???, had been contacted by the Norwegian Nobel Committee 10 minutes before the official announcement.

But she was suspicious.

Despite the enormous success of ICAN (International Campaign to Abolish Nuclear Weapons) in spearheading the first global treaty to ban nuclear weapons in July, Ms Fihn suspected the call was a hoax.

"Our colleague in Geneva wasn't sure if it was a genuine call or not," said Mr Wright from his office at Victorian Trades Hall on Saturday. "It took us all by surprise. She texted through to say, 'We won it, but don't tell anyone because it could be a hoax'."

Ten minutes later, the announcement came through on the webcast. ICAN's website crashed, as people around the world started researching the organisation named as the "driving force" behind the signing of the historic UN treaty.

ICAN launched in Melbourne in 2007 and comprises paid members: three in Geneva, one in Melbourne and one in Sydney. By creating a global campaign coalition with 468 partner organisations in 101 countries, ICAN has successfully lobbied politicians and galvanised the public to oppose nuclear weapons.

"I guess it's testament to how a small group of people can have a big impact on the world stage," said Mr Wright, ICAN's first volunteer.

"It's a tribute not just to our work over the past decade, but to the work of activists around the world in previous decades. They're all part of the broader international campaign to abolish nuclear weapons."

The group is funded by private donors and runs on a shoe-string budget (the Asia-Pacific arm's annual budget is $160,000).

The prize money of $1.42 million will help the group ramp up efforts to urge countries to sign and ratify the treaty, which was adopted by 122 countries on July 7, and signed by 53 nations in September.

Nuclear-armed states including the United States, Russia and China kept out of the talks, while the Australian government has refused to sign the treaty and has boycotted negotiations.

Just two weeks ago, an ICAN activist climbed to the top of the Department of Foreign Affairs and Trade in Canberra building and held a banner demanding that Foreign Minister Julie Bishop sign the treaty.

"This is the greatest threat to humanity and to the entire planet," said Mr Wright.

"It's been a huge disappointment for us that the Australian government has boycotted the negotiations ??? It has been a very active opponent of this process because of its support for US nuclear war fighting."

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Through a spokesman, Prime Minister Malcolm Turnbull declined to congratulate ICAN on the win, but acknowledged its commitment to the cause.

"The Australian government shares, with the international community, the goal of a peaceful and secure world free of nuclear weapons," Mr Turnbull's spokesman said.

"We acknowledge the commitment of ICAN and its supporters to promoting awareness of the humanitarian consequences of nuclear weapons.

"However, Australia's position on the Treaty on the Prohibition of Nuclear Weapons is clear and well known. In our view the treaty will not advance nuclear disarmament and will not enhance security but may well harm the cornerstone Nuclear Non-Proliferation Treaty regime.

"So long as the threat of nuclear attack exists, US extended deterrence will serve Australia's fundamental national security interests."

ICAN co-founder Tilman Ruff - who is now winning the prestigious prize for the second time - has called on Australia to oppose nuclear weapons, particularly in the face of North Korea's escalating missile and nuclear tests and US President Donald Trump's inflammatory pro-war rhetoric.

Associate Professor Ruff said the current political climate bore similarities to the Cold War, when tensions prompted him in the mid-1980s to buy a share in a farm in Lima East in Melbourne's north-east to escape to in the event of nuclear war.

In 1985, the infectious diseases and public health physician became involved in the International Physicians for the Prevention of Nuclear War. That year, the organisation won the Nobel Peace Prize for triggering an "awakening of public opinion" on the catastrophic health consequences of atomic warfare.

Teaching the world about the dangers of nuclear war has been something of a calling for Professor Ruff.

"Once you understand what nuclear weapons do and are, there is an urgent need to get rid of them. The risks of their use exist as long as the weapons do," he said.

"There should just not be the capacity for any single person to end the world as we know it in an afternoon. The only cure is prevention."

With Michael Koziol