London, May 11 : Aid for Cyclone Nargis survivors in Myanmar is trickling in sporadically, and the United Nations fears that only a quarter of the survivors have received aid so far.

According to a BBC report, the U.N.'s World Food Programme (WFP) says three plane-loads were flown in on Saturday and appear to have been released for distribution.

Leaders in Myanmar are being criticized for holding a referendum when close to 1.5 million people may have been affected by the disaster.

Voting took place in two-thirds of the country on Saturday, but was postponed for two weeks in the worst-hit areas - including the Irrawaddy delta and Rangoon, the main city.

The country's ruling generals say the vote will pave the way for democratic elections in 2010, while the opposition says it is intended to entrench military rule.

The UN, which has launched a 187 million dollar appeal for aid, says those in the worst-affected areas urgently need food, shelter and medical aid.

Burmese state media, however, claims that only 23,335 people have died, but the UN fears the toll could be about 100,000.

The WFP's latest deliveries included high-energy biscuits, shelter materials, and communications and office equipment. The agency said it hoped the authorities would soon release Friday's two deliveries.

Earlier on Saturday, a convoy from the UN refugee agency, UNHCR, crossed into Myanmar from Thailand with 22 tons of tents and other humanitarian supplies.

Joe Lowry, of the International Federation of Red Cross and Red Crescent Societies, was quoted by the BBC as saying that he hoped another seven flights would reach Myanmar before Monday.

Since the cyclone struck on 3 May, aid agencies already in the country have started relief efforts with supplies they had available and by buying from local sources. But they have warned of the supplies running out unless more aid is allowed into the country.

Aid has been flown in from China, India, Pakistan and Thailand, and the first US relief flight is expected to arrive on Monday.

But aid agencies claim that the Burmese government does not have the capacity to handle the scale of the relief efforts needed and must allow more foreign aid and disaster experts into the country.

The International Federation of Red Cross and Red Crescent Societies said thousands of people were homeless and are living in pitiable conditions. Hospitals, schools and other large buildings are crammed with the displaced.