YANGON (AFP) - - Frustrated world leaders condemned Myanmar's military rulers on Saturday, alleging negligence and possible crimes against humanity by refusing a massive foreign relief effort for the cyclone tragedy.

Just hours after the regime nearly doubled the toll of dead and missing to 134,000, the international community blamed the generals for the fate of up to 2.5 million survivors battling to stay alive two weeks after the storm hit.

The bitter criticisms appeared to mark a shift in tactics after more diplomatic pleas for a full-scale emergency operation fell on deaf ears, even though a second wave of deaths could lie ahead due to starvation and disease.

"This is inhuman. We have an intolerable situation created by a natural disaster," Prime Minister Gordon Brown of Britain, the colonial power of the country once known as Burma, told the BBC.

"It is being made into a man-made catastrophe by the negligence, the neglect and the inhuman treatment of the Burmese people by a regime that is failing to act and to allow the international community to do what it wants to do."

Deeply suspicious of any foreign influence that could weaken its 46 years of iron rule in Myanmar, the junta has insisted on managing the relief operation itself and kept most international disaster experts away.

But aid groups say the government cannot possibly handle the tragedy by itself, with hundreds of tonnes of supplies and high-tech equipment piling up in warehouses, bottle-necked by logistics and other problems.

The groups say even their own operations are short of fuel and the proper trucks to manoeuvre in a disaster zone where bridges are out, flooding has been heavy and new seasonal rains are deepening the difficulties.

Nobel Peace Prize winner Desmond Tutu wrote to Brown as well as French President Nicolas Sarkozy and US President George W. Bush, calling on the UN Security Council to authorise aid drops over the objections of the generals.

"The refusal of the Burmese military regime to accept full, adequate humanitarian aid from the international community is nothing short of criminal, and unprecedented in recent history," Tutu said.

Jean-Maurice Ribert, France's UN ambassador, told a meeting of all members of the United Nations that the situation was turning "slowly from a situation of not helping people in danger to a real risk of crimes against humanity."

Faced with the mounting criticism, the junta flew some diplomats and aid workers Saturday into the heart of the disaster zone -- which has been all but sealed off to the outside world.

But the secretive leadership, who rule from a remote bunker town and are rarely seen in public, are long accustomed to presenting propaganda at odds with the reality of this impoverished nation.

"What they showed us looked very good," said Chris Kaye, Myanmar director for the UN's World Food Programme, after taking one of the state-run tours. "But they are not showing us the whole picture."

The junta has blocked journalists from getting to the southern Irrawaddy Delta, the rice-growing region hardest hit when Cyclone Nargis hit on May 2-3, bringing powerful winds and massive waves that wiped whole villages away.

But those who have got through have returned with tales of unspeakable misery -- thousands begging for food, corpses rotting in swamps and countless reports from people saying they had received little or no aid from the government.

Aid agency Save the Children said up to 2,000 children were lost and unable to find their parents.

Survivors have reported that the military was pushing survivors out of temporary shelter in monasteries, whose revered Buddhist monks helped lead massive protests against the regime last year.

Navy ships from France and the United States are positioned off the Myanmar coast stocked with emergency supplies, but the regime has denied them entry.

The regime is said to fear a possible invasion by the United States, which has criticised Myanmar for keeping democracy activist Aung San Suu Kyi under house arrest -- and for its slow moves toward elections promised in 2010.

The government said this week that 99 percent of eligible voters had cast their ballots last Saturday in a referendum it said approved a new constitution which would bar her from office.

Her party rejected the result and said the vote should never have been held amid the cyclone tragedy. The regime has scheduled round two, in the disaster areas, on May 24.