In this city's Revolution Square, which was dressed up for May Day in acres of red bunting and a giant billboard painting of Marx, Lenin and Engels, Ethiopia's military leader accused western "imperialists" today of waging "psychological warfare" against his people.

"They vilify and oppose all our positive efforts against famine and pretend to sympathize with our people," said Mengistu Haile Mariam, referring to unnamed imperalists who he said "sneer at the socialist goal for which we struggle."

Mengistu's May Day speech, part of a celebration here that featured goose-stepping soldiers, martial music and a parade of dungaree-clad, slogan-chanting workers, came about six months after the beginning of an unprecedented worldwide effort to rescue the 7.9 million people threatened by the worst famine in Ethiopia's history.

More than 100,000 tons of food a month, together with medicine, blankets, clothes and temporary shelters, are now arriving at Ethiopia's ports, most of it from western countries, including the United States.

While not mentioning this aid, Mengistu detailed in his speech what he said was "a multidimensional" campaign by imperialists against his country's famine relief program.

Mengistu's attacks on "American imperialism" during last year's May Day speech provoked the U.S. charge d'affaires here, David A. Korn, to get up and leave the reviewing stand in Revolution Square. During today's speech, which made no specific reference to the United States, Korn remained in his seat.

Mengistu said that through the use of "subtle propaganda," the enemies of Ethiopia "denigrate" the government's resettlement program, which since November has moved more than 330,000 people from the drought-stricken central highlands to the country's southwest.

Western donor governments, particularly the United States, have criticized the resettlement program for moving too fast and have questioned whether it is voluntary, as the government here insists.

Referring to rebel wars in northern Ethiopia, Mengistu accused unnamed imperialists of using "mercenaries" to "challenge our country's unity by bleeding our people." In a program that Ethiopia considers in violation of its sovereignty, large quantities of U.S. food currently are being trucked through bordering Sudan to rebel-held areas in the north.

Sudan, in a policy that has strained its relations with Ethiopia, has allowed rebels of Eritrea and Tigray provinces to operate inside its borders. Mengistu said today that ending this support "is a key to improvement of the relationship between our two countries."

A senior delegation from the new military government in Khartoum visited Mengistu last weekend in Addis Ababa. Diplomats here said the talks centered on a possible deal in which Sudan would stop supporting rebels in Ethiopia in return for Ethiopia ending its support of rebels who now control the southern half of Sudan.

Mengistu's speech came one day after two senior western relief officials here said that Ethiopia's largest famine relief camp had been evacuated and burned during a three-day period ending Tuesday.

With the government here taking the day off for May Day celebrations, there was no official government information about the fate of more than 52,000 former residents of Ibnet camp who now are walking in the rugged mountains of Ethiopia's central highlands.

These people, including several thousand children under 5 and thousands of adults weakened by malnutrition, were forced by Army troops to abandon the camp and told to return to their farms, according to the two relief officials who flew to the camp Tuesday.

Relief workers at Ibnet, located in Gondar Province, reportedly have said that many of the people will die before they can reach their homes.

The decision to evacuate the camp reportedly was made by local leaders of the Workers' Party of Ethiopia in Gondar. One relief official said today that top government officials in Addis Ababa were surprised by news of the evacuation of the camp.

Kurt Jansson, U.N. assistant secretary general for emergency operations in Ethiopia, said tonight that a reconnaissance helicopter flight on Thursday would survey the area around Ibnet to try to locate those who were forced to leave the camp.

Jannson said that, based on the reconnaissance report, efforts could begin to airlift food and other assistance to the former residents of Ibnet.