Ugandan officials ordered extreme security measures this evening as invading forces reportedly gained control of the high ground overlooking the capital, Kampala, and the international airport at Entebbe.

Radio Uganda reported early Monday morning that the invading forces had cut the road between Kampala and Entebbe but it gave no indication of the whereabouts of President Idi Amin, according to news service.But one Ugandan government official called reporters in Nairobi, Kenya, to say Amin was trapped at his official residence in Entebbe. His report could not be confirmed.

The radio report meant the bulk of Amin's army and 1,000 Libyan troops and Palestinian advisers were cut off from any further resupplies from the outside world via the Entebbe Airport, located on the edge of Lake Victoria.

A Military Council announcement broadcast on Radio Uganda imposed a 12-hour curfew -- from 6 p.m. to 6 a.m. -- throughout the country during which no one is allowed to use electricity. It also said that Entebbe Airport is closed and foreign planes that violate the country's airspace without special permission will be shot down.

The announcement declared that "anyone who cooperates with the enemy" or "violates roadblocks" will be "treated as a traitor," presumably meaning that he will be shot.

These are the most drastic security measures taken so far by the Amin government which, for five months, has been battling an increasingly powerful army composed of Tanzaian troops and dissident Ugandans. The antigovernment forces already have established a vast "liberated" area in the rich coffee-growing area of southern Uganda and have set up a rear base at the town of Mawaka.

Today's emergency measures were precipitated by the invading forces' occupation of Mpigi Thursday. Mpigi sits on a hill just 20 miles outside Kampala and even closer to Entebbe, bringing these last strongholds of the Amin government within the range of enemy artillery. Residents of Entebbe reported hearing several explosions over the weekend, apparently incoming artillery as guns placed at Mpigi take range.

All indications are that while the forces opposed to Ugandan leader Idi Amin grow in numbers each day, Amin's army is falling increasingly into disarray. A variety of sources indicate that large numbers of Ugandan soliders are deserting. Western intelligence sources stated late last week that Amin has only two battalions or about 2,500 soldiers left out of his army of 20,000 at the beginning of the war.

In addition, reliable Ugandan exile sources say the Ugandan Army suffered very heavy casualties two weeks ago in the battle at Lukaya, 50 miles outside Kampala.According to one observer, "The battle of Lukaya may turn out to have been the turning point in the war."

Amin clearly has been anticipating a showdown north of Mpigi. For several weeks Ugandan officials reportedly have been going through the area between Mpigi and Kampala and telling villagers to evacuate "to make way for the two armies." Sources in Kampala report that in the last few days leaflets have been clandestinely distributed warning people to leave town.

It appears likely, however, that the Tanzanian-backed anti-Amin forces will delay the final military assault until after the completion of the political process of forming a transitional government capable of administering the country and organizing democratic elections after Amin falls. Ugandan exiles from around the world have been meeting since Friday in the northern Tanzanian town of Moshi to try to smooth over their differences and put together a transitional government.

Reports from the meeting are sketchy because all journalists have been barred. According to reliable sources, however, supporters of former Ugandan President Milton Obote, whose forces form the bulk of the anti-Amin resistance army, have walked out of the meeting.

Obote has been hostile toward the Moshi meeting, which he sees as the beginning of a process that will not only hasten Amin's downfall but also block his own chances of regaining the presidency. Obote refused to attend the meeting and was persuaded to send representatives only after considerable arm twisting by the Tanzanians.

Obote, who was desposed by Amin in a coup eight years ago, is not overly popular with many of the exiles. Ironically, despite his soliders' recent military successes, his political role seems to be diminishing.

According to a report in today's Nairobi Times, the Moshi conference has set up a provisional government in Masaka headed by Yusufu Lule, the former chancellor of Makerere University.

Observers here say Lule, who is in his 70s and has not been closely associated with any exile organization, is well respected and an "acceptable" compromise candidate to the widely varied exile organizations. He also is said to be on good terms with top Tanzanian officials.