Aid groups said Sunday that supplies trickling into cyclone-hit Myanmar were far less than was needed, as the faltering relief effort suffered a new blow with the sinking of a Red Cross boat.

The boat, carrying vital supplies of drinking water, rice, and purification tablets, hit a submerged tree trunk as it travelled by river through the disaster zone. Much of the aid was lost, but no one was injured.

"Apart from the delay in getting aid to people we may now have to re-evaluate how we transport that aid," said Michael Annear, disaster manager in Yangon for the International Federation of Red Cross and Red Crescent Societies.

Supplies have slowly begun to make their way into isolated Myanmar, but relief workers are frustrated over restrictions by the ruling junta, which has refused to allow foreign experts in to direct the recovery effort.

"Some opening-up on the part of the authorities is allowing us to get these materials to their destination," said Stephan Goetghebuer, director of operations of medical charity Medecins Sans Frontieres (MSF).

"But it's no more than a drip-feed, really, given a serious response is more than required. We still need more back-up aid and personnel ready to leave."

A United Nations flight from Italy carrying water purification equipment and other supplies landed in Yangon, but three UN disaster assessment experts were still waiting for visas in Thailand.

In an indication of the tight controls the junta is maintaining, two of the three had their UN travel documents refused by Myanmar officials at Yangon airport when they tried to enter the country Thursday.

Other arrivals were a cargo plane chartered by the International Committee of the Red Cross, and a Greek air force plane with a cargo of tents, food and medicine.

Greece said its foreign ministry staff will stay in Yangon to make sure the the aid reaches those it is intended to help, and that a second military transporter is due to land on Tuesday.

Cyclone Nargis, which smashed into the rice-growing Irrawaddy Delta region in the country's south on May 3, left nearly 62,000 people dead or missing, according to a government toll.

The military government's refusal to open its doors has infuriated aid groups and foreign governments who say that unless they have free access, the toll from the disaster will rise dramatically as hunger and disease set in.

"It's not true that nothing is happening at all, but not enough is happening," said Frank Smithuis, Myanmar country manager for MSF.

Two MSF cargo planes carrying 75 tonnes of shelters, water-treatment equipment, first-aid supplies and food are en route from Europe and due to arrive on Monday.

French charity Medecins du Monde said Sunday that Myanmar authorities had agreed to let it distribute its aid, which was arriving Monday.

The international community has spoken out in increasingly concerned tones over Yangon's apparent sluggishness or suspicion when it comes to taking up offers of overseas and even non-governmental aid.

British Foreign Secretary David Miliband accused Myanmar's ruling generals of "malign neglect," warning the aftermath of its cyclone was a "catastrophe of genuinely epic proportions."

And Europe's aid commissioner Louis Michel, while praising "signs of improvement" in Myanmar's cooperation, urged Yangon to let more relief workers in.

"The (European) Commission is ready to give more but the funds won't be much use without professional delivery on the ground," he said.

Sarah Ireland, East Asia director for development charity Oxfam, warned that all the factors were in place for a public health crisis that could multiply diplomats' estimates of 100,000 dead by up to 15 times.

"It's a perfect storm of factors such as a lack of water, sanitation, predicted heavy rain over the next week, lack of food as well as outbreaks of disease," she told a press conference.

earlier related report
'Drip-feed' of aid but Myanmar still desperate
The pace of aid deliveries into Myanmar picked up Sunday, but as thousands of starving cyclone survivors turned out on the roads to beg for food and water, experts said far more was needed.

Myanmar's ruling generals, who have refused to allow foreigners in to direct the relief effort, were also condemned for holding a national referendum at the weekend despite the devastation in the country's south.

The regime hailed a "massive turnout" in the vote to ratify a new constitution, even as aid groups warned the official toll of nearly 62,000 dead or missing could rise unless it focused on helping survivors immediately.

An AFP journalist who travelled from Myanmar's main city Yangon to the southern delta, which was ground zero in the disaster, reported there were at least 10,000 people lining the sides of the road, waiting for help.

Hungry and thirsty, their numbers are building fast -- and the only help arriving was from religious groups and well-wishers who pulled up to unload packets of rice and noodles.

Elsewhere, corpses still lay rotting in waterways, jostling against the bloated carcasses of buffaloes and other livestock, as children scavenged for fish in polluted canals.

The regime announced Sunday that the official death toll had risen by 5,000 to 28,458, with 33,416 people missing, but diplomats have warned the toll likely exceeds 100,000. The United Nations has said that 220,000 are missing.

Despite the serious hurdles including the impounding of tons of supplies at Yangon's airport, planes laden with goods began thundering into the country, including a flight chartered by the International Committee of the Red Cross, and a Greek air force plane with a cargo of tents, food and medicine.

Despite deep enmity between the two countries, a United States military plane has also won permission to fly into Myanmar with relief supplies and is due to land on Monday.

"Some opening-up on the part of the (Myanmar) authorities is allowing us to get these materials to their destination," said Stephan Goetghebuer, director of operations of medical charity Medecins Sans Frontieres.

"But it's no more than a drip-feed, really, given a serious response is more than required," he said.

Europe's aid commissioner Louis Michel praised "signs of improvement" in Myanmar's cooperation, but urged Yangon to let more relief workers in.

"The (European) Commission is ready to give more but the funds won't be much use without professional delivery on the ground," he said.

The faltering relief effort suffered another setback when a boat carrying Red Cross supplies sank after hitting a submerged tree trunk. The crew, including four Red Cross workers, managed to get to safety.

Much of the cargo was lost but local people and the crew managed to salvage some of the items on board, which included water, clothes, soap, household goods and medical goods.

"Apart from the delay in getting aid to people we may now have to re-evaluate how we transport that aid," said Michael Annear, disaster manager in Yangon for the International Federation of Red Cross and Red Crescent Societies.

State television meanwhile continued to show pictures of the generals casting their ballots in a vote that critics said was intended only to strengthen their 46-year grip on power.

"The question that has to be asked is whether people turned out voluntarily or not, and whether they got to vote according to their minds," said Sunai Phasuk of Human Rights Watch in neighbouring Thailand.

"In any authoritarian country, they try to legitimise themselves through the ballot box," he said.

The poll -- held in all but the areas worst-hit by the cyclone, which will vote later in the month -- went ahead despite stark warnings for the estimated 1.5 million people at grave risk following the disaster.

Many are still without food, clean water, shelter and medical supplies, and the regime's insistence that it is "not ready" to let in foreign aid workers has infuriated much of the international community.

"We have the skills and expertise to save lives," Sarah Ireland, regional director of Oxfam, one of many aid groups blocked by the junta from sending in its personnel, told a news conference in Bangkok.

"We are here to help," she said, warning that all the factors were in place for a "public health catastrophe" which could multiply the estimates of 100,000 dead by up to 15 times.