Chris McGreal , who witnessed the genocide in Rwanda in 1994, reports on the uncovering of UN failures to halt the murder of 800,000 Tutsis

The last time Helena Nwitizina saw United Nations soldiers they were driving off to rescue white people. She was not among those who begged the Belgian peacekeepers to administer a quick death rather than abandon them to the men with machetes. But the 30-year-old petrol pump attendant was no less terrified.

A few hours later Nwitizina was one of the few people to crawl out of the first big massacre of the Rwandan genocide.

'We could not believe that the United Nations was just going to let us die. We were always hearing on the radio how they were there to help us. But when the killers were looking us in the eye and saying we were going to die what did the UN do? It saved white people,' she said.

Last Thursday, Kofi Annan expressed his 'deep remorse' for the UN's shortcomings in Rwanda five years ago after an independent report offered a damning assessment of the organisation's failure to even attempt to halt the murder of 800,000 Tutsis.

Annan was not spared. He was head of UN peacekeeping in 1994. The report criticises him for ignoring repeated warnings that a genocide was in the offing. It also condemns members of the Security Council, including Britain but principally the United States, for blocking calls for rapid intervention.

The most prescient warning came from the head of the UN contingent in Rwanda, General Romeo Dallaire. It told of a plan to kill 1,000 Tutsis every 20 minutes.

It also said the murderers intended to drive the UN out by killing some of its Belgian peacekeepers. Annan's office responded by telling Dallaire to take the information to the very government planning the slaughter.

Ten Belgian soldiers were duly butchered on the first day of the genocide. As the extremists hoped, Belgium insisted on pulling its troops out.

When the order came to wind down the mission, the UN political adviser in Kigali, Shahryar Khan, turned on his bosses in New York. 'Ten Belgians are dead, so you don't give a damn that thousands of Africans are about to be slaughtered,' he said.

The Belgian commanding officer in Rwanda, Colonel Luc Marchal, later said he considered the order to pull out an act of cowardice. 'We were perfectly aware of what was about to happen. Our mission was a tragic failure. Everyone considered it a form of desertion. Pulling out under such circumstances was an act of total cowardice,' he said. The first few thousand died within hours of the start of the UN withdrawal.

Lieutenant Luc Lemaire was in command of a contingent of Belgian troops guarding about 2,000 Tutsis at a technical school in the capital, Kigali. They sought shelter there precisely because of the UN peacekeepers, but Lemaire was ordered to abandon the school. The UN denied it, but the Belgian officer says his men were redeployed to help evacuate white foreigners. 'We received a series of clear messages that showed me that the UN's mission was to be the evacuation of expatriates to the airport,' he said.

As the Belgian soldiers pulled out of the school grounds, groups of Tutsis rushed their vehicles, clinging to the doors in an attempt to stop the troops leaving. Nwitizina was among them.

'We knew the UN was abandoning us. We cried for them not to leave. Some people even begged for the Belgians to kill them because a bullet would be better than a machete,' she said.

The Belgians fired into the air to drive the refugees back. The Tutsis decided their best hope was to walk across the city to the UN headquarters. But they were intercepted by the Hutu army and militia and diverted to a gravel pit.

There, about 2,000 Tutsis were murdered just hours after the UN troops abandoned them. Nwitizina was among the few survivors.

'The army started throwing grenades and shooting. Then the interahamwe came in with machetes and bayonets. Most those who tried to escape were cut down. It went on for hours. 'Once the interahamwe left I managed to climb out from under the bodies. I thought I had been shot in the legs because I could not feel them but it was just the weight of corpses.'

The UN also left behind its Rwandan staff. When it came to preserving lives, headquarters in New York meant foreigners not locals.

Even where Tutsis were able to clamber on board UN lorries, it was no guarantee of safety. The interahamwe pulled victims off at roadblocks and butchered them in front of French or Belgian soldiers who said they had no mandate to intervene.

There was never much doubt as to what was unfolding, but Washington and Britain were at one in their refusal to spend more money by expanding the peacekeeping force in Rwanda and beefing up its mandate.

After the US debacle in Somalia, when an American-led force slaughtered hundreds of civilians in a crude bid to impose order, and lost 18 men in the process, the White House issued a directive setting out the conditions for future US peacekeeping operations. Rwanda met none.

The White House was at least frank about its policy.

Gerald Gahima, a representative of the Rwandan Patriotic Front, which fought the Hutu extremist government, tried to lobby UN ambassadors, including Sir David Hannay, Britain's representative on the Security Council. 'I didn't get the impression he cared at all. We might have been talking about slaughtering chickens.'

All the Security Council managed was a tepid statement calling for a ceasefire. It was to seal the fate of hundreds of thousands of Tutsis.

Once it was clear that the UN was abandoning Rwanda, the killing spread rapidly. From Kibuye in the west, where 17,000 people were murdered in two days in the local church and stadium, to Butare in the south, where President Theodore Sindikubwabo personally launched the massacres with a speech.

Dallaire later said he could have stopped the genocide in Kigali with 5,000 troops and so prevented it spreading.

Annan says the lessons have been learnt. Helena Nwitizina doubts it. 'Do you think anything has changed? We are still poor Africans. Why should they want to help us now when they would not help us before?'