On Saturday Chan and Sukumaran were given the obligatory 72-hours' notice of their executions by Indonesian authorities. 

Brisbane residents gathered at the Cathedral of St Stephen joining people with heavy hearts around Australia in taking part in last-ditch pleas for clemency.

Australians Against Capital Punishment spokesman Don Sinnamon said there was still a glimmer of hope despite many in the crowd's sombre resignation.

"Until that firing squad pulls the trigger there's hope. As long as there's breath, there's still hope," Mr Sinnamon said.

He remained adamant that the decision to execute the men was counterproductive to Indonesia truly tackling its drug problem.

"Their (Chan and Sukumaran's) stories of reform and staying out of the drug trade are much better as living ambassadors than as corpses," he said.

Yet keeping hope alive in these trying times is proving difficult for many, including long-time activist Camilla Cowley.

"For all of those years of campaigning, I think in my heart of hearts I never really believed it would come to this, but it has", a visibly saddened Ms Cowley said.

"I suppose, personally, I don't have any hope."

It's this sadness that seemed to pervade through the modest crowd, which came together on short notice. Labor Senator Claire Moore echoed the sentiments of many.

"In a recent speech in Parliament I said I was tired of candlelight vigils – every time it means that someone is under sentence. For me, it's personally appalling," Senator Moore said.

"It's hard to be hopeful, and we've lived with this for years."

Yet the senator wouldn't be drawn on media reports claiming Indonesian judges had sought payment from Chan and Sukumaran in exchange for a lesser sentence, saying now was not the right time to raise such allegations.

"To bring up these issues of alleged corruption at this time I think takes away a little bit from the pain that is going on. If there are allegations of corruption in the system then they should be investigated but to focus on that now is not what I think is most important," she said.

"The focus must be in showing that the death penalty is wrong. It doesn't stop crime."

Those who were unable to attend vigils being held across Australia on Monday can sign petitions from Amnesty and the Mercy campaign that, according to Mr Sinnamon, would be forwarded to the Indonesian government 'pretty much instantly'.

People can also Tweet using the hashtag #keephopealive or #istandformercy.

"Anything that you can do to raise the issue and show your opposition to these sentences helps," Mr Sinnamon said.