First, the police fire tear gas, then rubber bullets. As protesters flee, they move on to live rounds. One man, wearing only a pair of shorts, stops to raise his hands in surrender. He is knocked to the ground and given an extended beating by eight policemen in black body-armour and helmets.

Demonstrators getting worked-over by the rifle butts and truncheons of Peru's security forces turn out to be the lucky ones, though. Dozens more were shot as they fled. You can see their bullet-ridden bodies, charred by a fire that swept through the scene of the incident, which has since been dubbed "the Amazon's Tiananmen".

The events of Friday, 5 June, when armed police went to clear 2,000 Aguaruna and Wampi Indians from a secluded highway near the town of Bagua Grande, are the subject of a heated political debate. They have sparked international condemnation and thrown Peru's government into crisis.

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Yet until today, details were shrouded in mystery. Now, pictures have emerged. They were taken at the scene by two Belgian aid workers, Marijke Deleu and Thomas Quirynen, and provide compelling details of the chaotic confrontation that killed a reported 60 people, many of them unarmed, with vast numbers still unaccounted for.

"At first, we saw police firing guns and tear gas at a mass of protesters," said Ms Deleu, who reached the highway at 7am, an hour after heavily armed police arrived at the location, 870 miles north of Lima. "Then we saw them beating and kicking people detained on the ground. Later, they shot people in the back as they started fleeing."

A dossier of photographs, many too graphic to be printed in this newspaper, will be shown to MPs at the House of Commons on Monday by Ms Deleu and Mr Quirynen, who are volunteers for Catapa, a Flemish organisation supporting indigenous communities in Peru, Bolivia and Guatemala.

Called Death at Devil's Bend, it attempts to explain what happened when police tried to evict the indigenous tribespeople, who had been blockading the road for several weeks in protest at new laws allowing energy and mining companies to exploit swaths of their ancestral homelands.

One series shows police stopping a passing ambulance. They force four injured protesters out of the vehicle, and beat them for several minutes, claiming, without any apparent justification, that their vehicle was carrying concealed weapons. Another, taken later in the day shows rows of wounded being treated in local hospitals. Nineteen are at Bagua Grand; 47 in Bagua Chica. Many have heavy bruising, and bandages covering bullet wounds.

"Several people said they had been shot while they were fast asleep," said Ms Deleu. "They claim the police woke them up by opening fire. One of the bodies had a bullet wound in his shoulder, which suggested to me that he'd been shot while lying down."

Further pictures, which will only fuel rumours of a government-orchestrated cover-up, show twisted corpses of native Indians lying by the side of the road. When tribal leaders tried to collect them, they came under fire and were refused access. By the next day, the corpses had disappeared.

The Peruvian President, Alan Garcia, has claimed 32 people were killed in the incident, of which 23 were police officers. However human rights lawyers and news reports put the number of confirmed deaths at closer to 60, and say hundreds are still missing.

Until this week, many international observers have been unable to visit the region because of a curfew. Pressure groups have accused security forces of burying and burning corpses to hide the extent of the death toll.

"There needs to be an independent investigation to establish exactly what happened," said Jonathan Mazower of Survival International, which will today publish Ms Deleu and Mr Quirynen's dossier on its website. "Our initial reaction to these dramatic photographs is that they may provide the first impartial account of what actually went on."

The pictures emerged as Alberto Pizango, the head of Aidesep, the organisation representing 56 of Peru's indigenous tribes, arrived in Nicaragua, after being granted political asylum. Last week, he was prosecuted for "sedition, conspiracy and rebellion".

Meanwhile Mr Garcia has been forced to suspend the introduction of laws allowing foreign companies to exploit the rainforest. His Prime Minister Yehude Simon resigned on Monday, joining populist minister Carmen Vildoso, who quit last week during a general strike in protest at the incident.