Myanmar's military rulers have been castigated by UN Secretary-General Ban Ki-moon.

Highly critical of the way the Myanmar government handled the delivery of aid for the victims of Cyclone Nargis, Secretary-General Ban said he was deeply concerned and immensely frustrated at the unacceptably slow response.

He added that the current crisis would be made much worse were Myanmar to face an outbreak of infectious diseases.

The UN leader said he had also repeatedly attempted to contact junta leader Than Shwe but had been rebuffed.

A number of foreign aid flights have already been given permission to land in Myanmar but the deliveries are not adequate.

The UN says five times the amount of aid is needed.

The military government has refused permission for most foreign aid workers in order to maintain its absolute control on the country.

So far, a total of 34 Myanmar visas have been granted to UN aid workers.

The government says that some parts of the country are still inaccessible for rescue teams.

The official death toll has risen to 32,000 and around 30,000 people are missing.