TO GRASP the true grimness of what is happening in East Timor, the best you can do is to sit down in the United Nations headquarters and listen in to one of the staff's walkie-talkies. Until yesterday, the traffic crackling out of them was alarming enough, but technical - reports on the movement of troops, direction of gunfire and movement of staff around the territory. Yesterday it was quite different. One of the little black radios is sitting next to me as I write this, and it is giving me the creeps. Last night, for the first time in East Timor, I felt afraid.

The UN Assistance Mission in East Timor (Unamet), which began with such optimism, appears close to collapse. This morning, perhaps - and if not today, in another day or two - there is a good chance Unamet will evacuate East Timor, leaving its people to an unimaginable fate.

Friday night was alarming, with automatic gunfire and grenades going off all over the capital, Dili, but yesterday began with a deceptive calm. Early on, it was decided to evacuate what the UN calls non-essential staff - 200 people, including police and military officers, leaving a staff of 84. The UN calls this "temporary relocation"; the official line is that in a few days, when things calm down, they will return.

The walkie-talkie suggested otherwise. The sense of doom began gathering yesterday morning, when the first evacuation convoy made its way towards the airport. Militiamen fired, shattering the back window of one of the cars. But the convoy made it to the first of five Hercules planes sent by the Australian government. That was only the beginning: in the afternoon a car carrying Australian diplomats was fired on as it travelled towards the Hotel Turismo to help a party of trapped journalists.

Close by, a scene was being acted out which even 24 hours ago would have been unthinkable. The home of Monsignor Carlos Belo, Roman Catholic bishop, Nobel Prize winner, and arguably the most respected East Timorese in the world, was assaulted by a combined force of militia and Indonesian soldiers. The army is no longer even attempting to keep up the pretence that it is independent of the militias. All day, they acted as one.

The bishop's house, where early-morning Mass is celebrated every Sunday, was burnt; he was taken away by the police and helicoptered out by them to the second city, Baucau.

Next door, the local office of the International Committee of the Red Cross was subjected to a two-hour barrage of automatic gunfire, aimed over the heads of 1,500 refugees. Finally the attackers burst in, pointing guns in the faces of women and children. The refugees were forced outside and 200 were marched off to a destination unknown. ICRC offices are treated across the world as diplomatic premises. Attacking one is equivalent to violating an embassy.

Last night diplomats in the Australian consulate were pinned down by sniper fire. "Repeated gunfire on the way to the airport," drawled the radio. "Numerous militias on the street and streets are impassable without armed escort," came another message. It was too dangerous to go outside, impossible to do anything all day apart from wander up and down the compound, talking to the police and military officers as they returned from their sorties, observing the mounting air of unease.

Several UN evacuees were weeping as they drove away. "We feel ashamed and guilty," said an American woman. "This evacuation should never have happened. Everyone knew there was going to be trouble and it should never have come to the point of bowing and scraping to the Indonesians. I was afraid for my life last night but we want to stay."

It was hard to face the refugees in the compound, whose numbers swelled yesterday as the Indonesian soldiers led new ones to the UN in an obvious attempt to make its work impossible by clogging it with additional mouths to feed.

The young Timorese man who worked last week as my translator is also sheltering here. "Richard!" he said as I walked by. "Tomorrow we go back to Hotel Turismo, yeah?" I found it difficult to look him in the eye.

Among the more suspicious, or astute, of the refugees, there is an overwhelming sense that something awful is going to happen.

Last night alarming and anonymous documents were being passed around the compound predicting the destruction of roads and bridges, and an attack on the UN by drug-crazed Indonesian troops.

During the campaign period for last Monday's referendum, which produced a 78.5 per cent vote for independence, Unamet mounted a vigorous and imaginative information campaign to assuage fears of retribution by the pro-Indonesia militias. "Unamet will stay on after the ballot," ran one slogan, "to make your choice a reality."

Late last night Ian Martin, the UN chief in Dili, admitted this was not true. "I cannot completely preclude the possibility that Unamet would have to pull out," he said, "if the security situation made it irresponsible to stay."

If that happens, there can be little doubt that a humanitarian catastrophe would ensue. In the chaos that followed Indonesia's first invasion of East Timor, in 1975, 200,000 people were murdered, starved to death or died of disease - a third of the pre-invasion population. Who can say whether the same thing will happen again?

But if it does, there will be a big difference this time. In 1975 Indonesia fought a war against a small, insignificant Portuguese colony. This time it is taking on, and beating, the representative body of the world.