Australia has given another $22 million for the victims of Cyclone Nargis but is warning of an impending calamity if help doesn't get to millions of suffering Burmese in the disaster's aftermath.

The total amount of Australian assistance now stands at $25 million and will be shared among United Nations' efforts and a variety of aid organisations.

More than a week after the cyclone devastated much of southern Burma, its ruling military junta is still refusing to let many foreign aid workers into the country, as well as impounding a number of flights of emergency supplies.

And, in the midst of the disaster, the junta carried out a constitutional referendum expected to entrench its authority, earning it further international scorn.

Foreign Minister Stephen Smith stressed the scale of the tragedy made it imperative for Burma's ruling regime to accept assistance.

"And it's a human tragedy on a mammoth scale which no one nation can handle," he told reporters.

With relief still to reach many of the victims of the cyclone, estimates of the death toll continue to grow as hunger and disease emerge as new threats.

Mr Smith repeated Australia's plea for the Burmese military to allow the international community into the country to help with disaster relief.

"If that assistance is not provided, then our great fear is that in the next few days... disease will take hold and the adverse consequences will be on an enormous, calamitous scale," he said.

More than 100,000 people are feared to have been killed - though some say the toll could be much higher - and at least 1.5 million people left homeless after south Burma was devastated by the cyclone's strong winds and storm surges.

Australia has been lobbying regional nations, particularly Singapore, the current chair of the Association of South East Asian Nations (ASEAN), to do what they can to convince the military junta to accept help.

"The single biggest important thing that can occur now is for the government of Burma to be persuaded that international assistance and international on the ground assistance ... is now paramount," Mr Smith said.

Aid organisations are still struggling to get visas for their relief staff entering Burma.

Sarah Ireland, Oxfam's regional director for East Asia, is part of a team of 10 from the organisation in Bangkok waiting for permission to enter Burma.

She holds significant fears for those Burmese still unable to access clean water and basic sanitary equipment.

"Those people living in the delta area are already poor and are going to be much more susceptible to diseases," she said.

Richard Bridle, from UNICEF, says a planeload of water purification tablets were on the ground in Rangoon but still had to go through customs, which could take a number of days.

"(It would help) if they could suspend some of these customs regulations so that we can get goods moved much quicker through the airports and if we could have specialists on the ground," he said.

Mr Bridle predicted the scale of the disaster was much bigger than current estimates.

"I still have a gut feeling that this is a disaster that is much bigger than we are currently imagining," he said.