By Aung Hla Tun

YANGON (Reuters) - Myanmar's military has started to bury cyclone victims in communal graves, villagers said on Wednesday, as Western nations pledged to keep aid flowing despite anger at its detention of opposition leader Aung San Suu Kyi.

The former Burma has been promised millions of dollars in Western help since Cyclone Nargis, but this cut no ice with the junta regarding the Nobel laureate, who has been under house arrest or in prison for nearly 13 of the last 18 years.

Officials drove to Suu Kyi's lakeside Yangon home on Tuesday to read out an extension order in person, but it was unclear whether the extension was for six months or a year.

"It is more likely one year," said a senior police source close to officials in charge of the 62-year-old's detention.

U.N. Secretary-General Ban Ki-moon, who just returned to New York from an aid mission in Myanmar, expressed disappointment but refrained from sharp criticism in light of the disaster, which left 134,000 dead or missing and 2.4 million destitute.

"The sooner restrictions on Aung San Suu Kyi and other political figures are lifted, the sooner Myanmar will be able to move toward ... restoration of democracy and full respect for human rights," he said.

Western nations were more forthright in their criticism of Suu Kyi's ongoing detention.

U.S. President George W. Bush said he was "deeply troubled" by the extension and called for the more than 1,000 political prisoners in Myanmar to be freed. However, the State Department said it would not affect U.S. cyclone aid.

Suu Kyi's National League for Democracy (NLD) won a 1990 poll by a landslide only to be denied power by the military, which has ruled the impoverished country for 46 years.

RED CROSS OFFERS TO HELP BURY DEAD

Few had expected Suu Kyi to be released, but the extension was a reminder of the junta's refusal to make any concessions on the domestic political front despite its grudging acceptance of foreign help after the May 2 cyclone.

Witnesses say many villages have received no outside help, and the waterways of the former Burma's "rice bowl" remain littered with bloated and rotting animal carcasses and corpses.

There has been no official word on plans to dispose of bodies, but villagers said soldiers brought about a dozen corpses to two sites for burial in Khaw Mhu, 40 km southwest of Yangon.

"The soldiers told everyone to shoo, to go away," one local woman said, adding that bodies were covered with "white powder" and then concreted over.

In Dedaye, also in the delta, a boatman said there were around 40 or 50 dead bodies in one waterway.

"We did the burial ourselves. If I know the dead person, I'll bury his body. If he knows the other dead person, he'll bury it." A World Health Organization official played down the immediate health risk from the corpses but said the issue needed to be addressed to prevent the sight of decaying bodies adding to the trauma of the survivors.

The Red Cross, which recovered thousands of bodies after the 2004 Indian Ocean tsunami, has offered to help in the grim task.

ACCESS IMPROVING, SAYS U.N.

Three weeks after the cyclone's 120 mph (190 kph) winds and sea surge devastated the delta, the United Nations said it had raised roughly 60 percent of its initial $200 million target for aid and relief workers were getting more access.

"We've reached just over a million people with some kind of aid," U.N. humanitarian affairs chief John Holmes told reporters.

Junta leader Senior General Than Shwe promised U.N. chief Ban last week that he would allow all legitimate foreign aid workers access to victims across the country.

Holmes said he did not know if all roadblocks had been removed, but the situation was better.

"There's still a lot of people out there who have received nothing or certainly not enough," he said.

(Additional reporting by Louis Charbonneau at the United Nations and Darren Schuettler in Bangkok; Writing by Ed Davies; Editing by Ed Cropley)