New York - UN Secretary General Ban Ki-moon said Monday that Myanmar's "unacceptably slow response" to international relief aid has resulted in less than one-third of victims of Cyclone Nargis receiving assistance from the outside.

UN officials said Myanmar's military regime has shown some cooperation 11 days after Nargis hit the country's low-lying southern delta, killing more than 31,000 people, with 34,460 people still missing, according to government figures. But they said the cooperation has been far from adequate.

"I want to register my deep concern - and immense frustration - at the unacceptably slow response to this grave humanitarian crisis," Ban said.

Ban said he had tried repeatedly, and unsuccessfully, to telephone Myanmar's top military leader, General Than Swe, since last week. Instead Ban has had to send two letters, the second one on Monday, through diplomatic channels.

John Holmes, the chief coordinator for the UN's emergency humanitarian office, said there had been no official contact between New York and the top military government leaders since Nargis struck May 3. Holmes said most contact had been made by UN relief workers on the ground with local officials in Myanmar.

Ban issued an appeal to the military regime "to put its people's lives first. It must do all that it can to prevent the disaster from becoming even more serious."

The 270,000 people in Myanmar who have so far received aid, out of an estimated more than 1 million cyclone survivors, have received "only the most rudimentary assistance."

The international community has been unable to organize large- scale logistical support, which ordinarily would go to any country hit by natural disasters. (dpa)