BANGKOK - Army-ruled Myanmar has stopped or restricted the delivery of U.N. food relief to 500,000 people, many of them children, as it cracks down on mass protests against the generals, the World Food Programme (WFP) said on Saturday.

All movements of food from the northern city of Mandalay, where monk-led protests began 11 days ago, have stopped, affecting WFP operations in Shan State and central areas.

"The immediate concern is in Mandalay, which is our logistics hub for delivering food assistance to vulnerable people that we serve in Myanmar," WFP Asia spokesman Paul Risley said.

Food deliveries have also slowed from the northwestern port of Sittwe, where tens of thousands of people have marched against 45 years of military rule, to people in north Rhakine State.

The hungry are mostly young children and people suffering from HIV/AIDS and tuberculosis.

WFP nutrition surveys have found child malnutrition rates of 60-70 percent in some pockets of the country, including impoverished border areas where ethnic groups have waged armed struggles against the junta for five decades.

Some 10,000 HIV-positive women become pregnant each year, giving birth to 3,000-4,000 children who are infected with the killer disease, the children's agency UNICEF says. The WFP has a three-year, $51.7 million plan to feed 1.6 million people in the former Burma, one of Asia's poorest nations, but has only received $12.5 million in donor funds so far.

"If the current shortfalls are not covered, it is to be expected that vulnerable families will face acute food shortages in an environment of rapidly escalating food prices," the agency said in a statement.