Soldiers of the Uganda army who have managed to escape into neighboring countries in recent weeks say that Soviet or other East European security experts are now working in President Idi Amin's State Research Bureau, a secret service group that is alleged to have been involved in many of the killings that have occurred in Uganda in recent years.

In addition, the soldiers say that more than 100 Soviet military instructors are training the Ugandan army in the use of tanks, missiles and artillery, and also act as flying instructors for the Mig squadrons.

They beleive that there are 2-to-4 squadrons of Mig-21s at the air base of Nakasongola, 70 miles north of Kampala. The advanced planes are flown by Soviets and Palestinians, the soldiers say, since no Ugandans are yet qualified to fly them.

According to the soldiers who have fled Uganda, Soviet experts have been brought in to act as "instructors and advisers" to the State Research Bureau.

It is possible that these instructors might be East Germans or come from other East European countries, since the soldiers do not distinguish between Soviets and others from Soviet bloc countries.

They confirmed that a number of Palestinians are also employed in the unit, but they dismissed as entirely inaccurate recent reports about Cuban military instructors or troops being in Uganda.

Admission into the Nakasonala air base is strictly controlled. Although the soldiers interviewed were unable to give any precise idea of the military build-up at this air base, they have provided information about the extent of Soviet military aid to Amin's army in other areas.

The soldiers report that army strength was 22,000 before the purges, which began last June after an attempt to assassinate Amin had failed. More than 7,000 soldiers have been killed, dismissed, retired or fled into exile in the last six months.

Of the remaining 15,000, 3,000 are southern Sudanese and 4,000-5,000 come from the Nubian parts of the West Nile, Amin's own tribal area.

These forces are concentrated in four units -- one in the capital, Kampala, and the others ringing the city approaches from the east, north and south-west, and control the country's most effective armaments. Thus Amin has minimized the possibility of other units acting against him.

Discipline is the basic problem. Amin personally encourages enlisted men to ignore orders from their officers and that is what occurs. When an officer files a charge, if the offender is a West Niler, southern Sudanese or Nubian, the commander takes no action.

Within the west Nile five trives in the army there are deep divisions between Moslem and Christian members and between various tribes.

The soldiers who have escaped say that other tribes in the army realize that once Amin has finished the Acholi and Langi, other tribes will also be purged, with the Teso probably the next in line.