The UN office for the Co-ordination of Humanitarian Affairs (UNOCHA) told Reuters that the government - which has indicated it will press ahead with a referendum on a new constitution on Saturday - was "having as much trouble as anyone else in getting a full overview" of the destruction.
"Roads are not accessible and many small villages were hit and will take time to reach," Terje Skavdal, the regional head of UNOCHA, said.
Teams of foreign aid workers were trying to assess the damage and aid needs, but their access and movements are restricted by the military.
"That is the existing situation for international staff. The way most agencies work is they use national staff who have more freedom to move," Skavdal said.
"We will have a dialogue with the government to try to get access to the people affected," he added.
The Forum for Democracy in Burma and other dissident groups outside of
Myanmar have also urged the military government to allow aid groups unfettered access to the country.
Myanmar was formerly known as Burma.
"International expertise in dealing with natural disasters is urgently required," said Naing Aung, secretary-general of the Thailand-based group.
"The military regime is ill-prepared to deal with the aftermath of the cyclone."
The government has declared the former capital of Yangon a disaster area after the storm's 190kph winds blew roofs off hospitals and cut off electricity supply.
|The government has declared the former |
capital of Yangon a disaster area
At least 351 people were killed, including 162 who lived on Haing Gyiisland off the country's southwest coast, military-run Myaddy television station reported.
Yangon, the Irrawaddy Delta, Bago as well as the Karen and Mon states were heavily damaged and have been declared disaster areas.
State-controlled television reported that 20,000 homes had been destroyed on Haingyi, an island in the Andaman sea.
A further 90,000 people on the island, the first part of the country to be hit by the cyclone, were left homeless, the government said.
Chris Kaye, the UN's acting humanitarian co-ordinator in Yangon, confirmed that "the Irrawaddy delta was hit extremely hard not only because of the wind and rain but because of the storm surge".
"The villages there have reportedly been completely flattened.''
Al Jazeera's correspondent in Myanmar said residents living in slums on the outskirts of Yangon have been among the hardest hit as many struggle to repair their homes before the next rainy season downpour.
| The storm blew roofs off hospitals and cut off |
electricity supply [AFP]
Resident of a slum of about 20,000 people said they were unlikely to receive help because the military government is not allowing NGOs to assist.
The owner of a house which lost its roof in the cyclone said he was not expecting assistance from local authorities as he struggles to feed a family of six after recently losing his factory job.
"No one has come to help us. Tomorrow I will have to look for another job because I need money to repair my house," he said.
It is unknown to what extent infrastructure destruction in the cyclone's aftermath will affect the holding of the May 10 referendum on a new charter backed by the ruling generals.
But the government indicated that it would proceed as planned.
"It's only a few days left before the coming referendum and people are eager to cast their vote," the state-owned newspaper Myanma Ahlin said on Monday.
The military bills the vote as one stage in a seven-step "road map to democracy", intended to culminate in multi-party elections in 2010.
The process has been labelled a sham by opposition groups who say the process is intended only to tighten the military's grip on power.