YANGON, Myanmar (CNN) -- Myanmar's military government began allowing aid agencies into the country Thursday to respond to the dire needs of those who survived the killer storm but is still being criticized for acting too slow.
A child sleeps on the floor as cyclone-affected families shelter in a school in western Yangon.
Myanmar Radio and Television (MRTV-4) announced that shipments from Bangladesh, China, India, Singapore, Italy and Thailand arrived Thursday at Yangon's international airport.
The state-run station said the military was using helicopters to deliver medicine, food and several generators throughout the Irrawaddy delta, the hardest-hit region, specifically in the areas around Bassein and Pyapon.
The secretive military junta that rules Myanmar says more than 22,000 people died after Nargis struck Friday into Saturday, but the top U.S. diplomat in the country said the toll could exceed 100,000.
Tim Costello, president of World Vision Australia, a Christian aid group, told CNN Thursday that the Myanmar government estimates 60,000 people are missing.
The tropical cyclone hit with a force equal to a Category 4 hurricane -- stronger than U.S. hurricane Katrina in 2005 -- with winds in some areas topping 240 kilometers per hour (150 mph).
It pummeled Yangon and the delta area to its south for more than 10 hours from Friday night into Saturday, dumping 20 inches of rain. Watch how a Buddha statue survived intact »
As many as 6 million people lived in the delta, the low-lying region that suffered the brunt of the storm.
CNN's Dan Rivers, reporting from a delta village, said one man told him he had lost his granddaughter, grandson, daughter-in-law and sister in the storm.
"There is absolutely no help here at all. We are the only outsiders they've seen -- no government soldiers and no aid agencies," Rivers said.
"There is talk of entire villages having been wiped out, of numerous bodies still floating in the water," he added. "We're not sure how long the refugees can last without help from the outside world." Watch Dan Rivers' report from Myanmar »
The U.S. Agency for International Development said Thursday that a 10-person disaster response team was in Bangkok, Thailand, awaiting the Myanmar government's permission to enter the country to assess the need there.
Also Thursday, the government of Myanmar refused entry to two of four disaster assessment team members who had previously been approved.
The U.N. Office of Coordination of Humanitarian Affairs reported Wednesday that 35 humanitarian teams from 18 countries were awaiting approval to enter Burma.
By Wednesday, USAID had allocated $3,250,000 in aid. Three U.S. Navy ships could reach the affected area within four days, but the Burmese government has not granted permission for the U.S. military to enter Burma.
The United Nations had promised to release more than $10 million from its Central Emergency Response Fund.
But a UNICEF spokeswoman said safe drinking water, shelter materials, water purification tablets, cooking sets, mosquito nets, medicine and sanitation supplies were all in dire need.
Juanita Vasquez, Myanmar officer in charge, told reporters in a conference call that survivors have found shelter in crowded, improvised camps set up in monasteries and schools. "People have left their houses, all their belongings and their livelihoods," she said.
UNICEF has deployed 10 teams to assess the problem and have begun to distribute enough medical supplies for as many as 500,000 people, she said.
In the two most heavily affected townships, three quarters of schools have been destroyed, she said. "This means that around 500,000 children cannot go to school on the first of June, when the school year starts," she said.
She said children are at highest risk of becoming quickly malnourished.
The fact that the port is closed means all supplies must arrive by air, said Patrick McCormick, emergency communications officer for the non-governmental organization.
"The government of Myanmar has to open the doors for us to come in and do our work," he said. "We need to increase the resources there, we need to increase the people there. This is a massive emergency."
U.N. Secretary-General Ban Ki-moon joined a chorus of people Thursday chastising the Asian government for waiting so long to let aid in.
"This is already the sixth day since May 2, when the cyclone hit Myanmar. We have lost several very vital few days at the outbreak of this cyclone. So this is already very late for the international community to take urgent first actions," Ban told CNN.
"Now, before it is too late, I would urge Myanmese officials to be flexible in dealing with these humanitarian issues with a strong sense of urgency." Watch Ban comment on the situation »
He also urged Myanmar to delay Saturday's scheduled referendum on a constitution backed by the junta. The government has postponed the voting in areas affected by the cyclone.
"It may be prudent to focus instead on mobilizing all available resources and capacity for the emergency response efforts," Ban said.
Aid workers, in particular, complained that supplies aren't getting into the country fast enough. Watch how some aid is getting through »
"This is a real worry for us," said Tony Banbury, regional director in Asia for the U.N. World Food Programme, which unloaded a plane carrying 7 metric tons of high-energy biscuits on Thursday.
Banbury said the situation in the delta is so desperate, "there is a real risk that there will be food riots, social disturbances, people attacking the convoys."
Of the 7 tons of biscuits, four tons were dispatched to Labutta in the delta, and the rest were to be distributed Friday by Medecins Sans Frontieres in the Yangon area, Chris Kaye, WFP director in Myanmar, said in a written statement.
Kaye said the government had cleared two more WFP flights to land -- one stocked with temporary warehousing and medical kits from the World Health Organization, and the other carrying 18 tons of high-energy biscuits donated by the Italian government. One ton of biscuits can feed 2,500 people for a day.
WFP workers were also carrying rice by truck to its new office in Labutta, and planned to distribute the food Friday. Two temporary warehouses have been set up to house the food, the group said. Look at satellite pictures of the damage by the flooding »
Relief agencies say authorities in Myanmar have been slow to issue visas to a small army of relief workers gathered in Thailand who are poised to fight a tide of hunger and disease.
People are sleeping outside with no food and no sanitation, and Costello fears the onslaught of diseases such as malaria, dysentery and cholera.
Even in the former capital, Yangon, people whose homes were destroyed are sleeping in temples and other public buildings, he said.
"It is still perilous, and it is a race against time, he said.
Costello said the military rulers would rather depend on groups already in the country, and also may be worried about possible interference in Saturday's voting. Learn more about Myanmar's recent history »
World Vision has 600 staff members based in Myanmar who have spread out to deliver 35 metric tons of rice, 4,000 gallons of water plus diesel fuel for generators that run pumps. Clothing, blankets and tarpaulins have been handed out to people living in and around Yangon.
Soldiers have tried to help, but the aftereffects are "devastating," Costello said. The organization is pushing the government to allow them to bring helicopters in to reach the delta faster.
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