THE village of Barranco del Tonina lies on the Sipapo river, a tributary of the Orinoco in southern Venezuela, about half an hour by fast launch from the nearest road. According to the local creation myth, its people—indigenous Piaroas—have fished these jungle rivers since the beginning of time. But lately their way of life has come under threat from armed outsiders with a history of raping the forest and harassing its inhabitants. In neighbouring Colombia, just a few kilometres away across a porous and sparsely populated border, the continent’s last big guerrilla organisation, the FARC, is on the defensive. Under sustained pressure from the armed forces in recent years, the insurgents have moved into Venezuela in large numbers. But what began as a tactical retreat has, with the apparent complicity of military and civilian authorities in Venezuela, turned into a multi-million-dollar criminal enterprise. The implications for the local populations have been deadly.

This is Amazonas state: bigger than Florida, but with a population of only 165,000, almost all of it in the state capital, Puerto Ayacucho. The hinterland of this vast territory, inhabited by scattered communities belonging to a score of indigenous peoples, is accessible only by light plane, helicopter or, for the most part, by boat.

Mining is banned by law, but gold and diamonds have for decades been extracted illegally, at a huge cost in deforestation and contaminated rivers. More recently, the contraband trade has expanded to include cocaine, guns and coltan (a mineral vital to the production of electronics), as well as petrol and basic foodstuffs, which are heavily subsidised in Venezuela. According to the state governor (an opponent of President Nicolás Maduro), the Catholic church and indigenous groups, the FARC is deeply involved in the mining and smuggling.

The Venezuelan government has consistently denied giving refuge to the guerrillas. In recent years the Colombian administration of President Juan Manuel Santos, keen to mend relations with Venezuela and pursue peace talks with the FARC, has gone along with this fiction. The Venezuelan national guard, whose tasks include border security, environmental protection and anti-smuggling operations, turns a blind eye.

But local people say the guerrillas have set up camps, imposed curfews and convened village meetings. Governor Liborio Guarulla complains that the FARC presence has reached the state capital. Just 5km from the official residence, he says, "they have held meetings with local leaders and business people to extort money".

Guillermo Arana of ORPIA, an umbrella group for indigenous organisations in the state, is among those who say the armed forces are not merely negligent but complicit. The guerrillas and the Venezuelan military, he complains, both exploit the illegal miners, "taxing" them in gold. "It’s the indigenous peoples that pay the price. The miners have no problems with the authorities."

Others point out that, while local people lack fuel for their boats and generators, barges laden with 200-litre drums of petrol pass freely through national-guard checkpoints. Each one costs less than $2 (at the official exchange rate) in Puerto Ayacucho. Up-river it can change hands for more than 400 times that price. Much is reported to cross the border, where it is heavily in demand for cocaine processing.

A flat-topped, vertical, sandstone slab called the Autana rises from the jungle across the Sipapo from Barranco. It is sacred, the Piaroas say, the stump of the tree of life, cut down by an evil deity. Under pressure from guerrillas, soldiers and common criminals, and running short of fuel and food, villagers in the area have begun to abandon their homes. According to the myth, new branches will one day sprout from the trunk and a new world will begin. That day seems a long way off.