Police said between eight and 10 masked attackers entered a gravel factory, threatened the caretaker, and fired weapons before setting fire to 12 trucks and four earthmovers.

The move was swiftly denounced by the governor of the Araucanía Region, where many Mapuche people live.

“This is a terrorist attack… it’s not a normal crime. It is a premeditated, planned act,” said Governor Luis Mayol.

At the scene, investigators found a pamphlet supporting Mapuche indigenous leader Celestino Córdova, who was convicted in 2013 of starting a deadly fire that killed an elderly farmer and his wife. He was sentenced to 18 years.

The leaflet was signed by CAM, a radical group dedicated to the recovery of former Mapuche lands that has staged several attacks on heavy machinery in the region, driving out forestry companies.

On a recent visit to the region, President Sebastián Piñera announced plans to expand Chile’s strict anti-terror laws which have been applied almost exclusively to Mapuche groups over their land protests.

The reforms broaden the harsh regulations imposed under the dictatorship of Augusto Pinochet (1973-1990) to fight against insurgent groups, but despite investigations into several attacks, police have been unable to prove they were carried out by terror groups.

Last year, activist leader Héctor Llaitul was jailed for six weeks on charges of carrying out several attacks, but he was acquitted after it emerged that the police had manipulated the evidence against him and 10 others in a case that raised questions over police conduct in the country’s south.

The state has long been accused of persecuting the Mapuche people, who centuries ago controlled vast areas of Chile but have since been marginalised.

The Mapuche account for 7% of Chile’s population, but hold only f5% of their ancestral lands.

They are considered the earliest inhabitants of parts of Chile and Argentina and have pursued historical claims against the authorities for territory and rights.