Bangkok - United Nations officials on Friday warned the Myanmar junta against premature resettlement of thousands of victims of Cyclone Nargis, warning that the policy could launch a second wave of the disasters.

Amid reports that Myanmar's military regime is instructing thousands of people displaced by Cyclone Nargis to return to their places of origin, senior UN officials warned that the policy could lead to disease outbreaks and more hardships for the 2.4 million people already affected by the catastrophe.

'The real risk of people going back prematurely is that they will have no access to essential life-saving services,' said Anupama Rao Singh, regional direction for UNICEF.

'They will pretty much become invisible to humanitarian workers, therefore facing all of us with a second wave of disease and disaster,' Singh told a press conference in Bangkok.

In fact, tens of thousands of people have been invisible to an international aid relief programme for the past four weeks in the wake of the May 2-3 cyclone.

International aid has reached about 41 per cent of the estimated 2.4 million people affected by the cyclone, with many of them stranded in remote areas in the sprawling Irrawaddy delta, the area hardest hit by the storm that left an estimated 133,000 dead or missing.

Access to the delta remains an issue, almost a week after Myanmar's junta chief Senior General Than Shwe promised UN Secretary General Ban Ki-moon that he would allow access to all international aid workers.

Terje Skavdal, Asia-Pacific regional director for the UN Office for Coordination of Humanitarian Affairs, acknowledged that Myanmar had sped up visa approvals for UN experts from two weeks to two days, and had allowed about 20 international workers into the delta since Than Shwe's promise.

'While we welcome the government's approvals of more entry visas for UN staff, we still urge them to show that same flexibility for NGO staff as well,' said Skavdal.

He said there was still no clear mechanism by which visas or travel papers into the delta were issued. Myanmar has allowed about 300 medical workers form Asian countries into the delta, but still blocks certain other foreigners from the area.

The Red Cross Red Crescent has been awaiting travel papers for six foreign experts on water-purification units desperately needed to provide clean water to survivors of the cyclone.

'There is a huge shortage of water in the delta,' Red Cross Red Crescent spokesman John Sparrow said.

'We've already deployed our water purification units in the delta, able to produce 1 million a day, but they are still awaiting our experts to become operational.'