Protesters scale Canberra DFAT building

A pair of protesters have unfurled a banner above the entrance to Canberra's foreign affairs department calling on Australia to sign the nuclear weapons ban treaty.

Wearing helmets and hi-vis vests, Gem Romuld, 30, and Papatya Danis, 27, climbed the front awning of the building on Wednesday morning.

Other supporters of the International Campaign to Abolish Nuclear Weapons held a giant copy of the prohibition treaty under the watch of Australian Federal Police and security guards.

"We need to put maximum public pressure on the Australian government and that's the purpose of this action today," ICAN board member Sue Wareham told AAP.

"The more the Australian people know that our government is not representing us on this, the easier it's going to be to get them to take this treat seriously."

She said the tensions on the Korean Peninsula demonstrated the urgency of the need to ban nuclear weapons.

The treaty, which prohibits a full range of nuclear weapon-related activities, was adopted in July and will open for signature this week at the UN.

Police later released the protesters from custody without laying charges.