More than one million homeless in Burma are battling to stave off disease and hunger, but the military government is maintaining tight limits on foreign assistance six days after a massive cyclone.

The UN estimates that at least 1.5m people in Burma have been ‘severely affected’ by Cyclone Nargis, which struck early Saturday. 

With death toll estimates near 100,000 and the clock ticking for those who survived, Burma's junta - long suspicious of the outside world - is under new pressure to fully open up to help from abroad.

The first UN relief flight has arrived in the country, but many more are waiting for permission from the military government to enter the country.

There are fears that many of those who survived the first tragedy may succumb to a second, falling prey to hunger and disease while the supplies that might save them languish nearby without permission to get in.

The UN said four disaster experts have received permission to travel to Burma, but there was no immediate word for hundreds of others awaiting a green light from the military, which has ruled the country since 1962.

State radio and television in Burma have reported a death toll of 22,980 with 42,119 missing and 1,383 injured in the world's most devastating cyclone since 1991.

Officials at the US embassy in Burma, which is also known as Myanmar, said there may be well over 100,000 deaths in the delta region.

That figure has not been confirmed, but is based on estimates by an international NGO.

In one town alone, Bogalay, at least 10,000 people were killed, according to a town-by-town list of casualties and damage announced by the military government.

24 countries have pledged €19m and more aid offers are expected. The UN emergency relief will contribute at least €6m.