Chile said it would invoke an anti-terror law from the dictatorship of Augusto Pinochet to punish a recent spate of attacks in the south linked to unrest by native Mapuches.

The controversial law triples the punishment for arson and illegal land occupation and has been used 16 times in the past decade, mostly against the Mapuche people who claim sovereignty over ancestral lands in southern Araucania region.

The United Nations recently urged Chile to stop using the law because it singles out the Mapuche and their social demands.

Deputy Interior Secretary Patricio Rosendo on Tuesday said the law will be used to deal with recent unrest in Araucania, including an attack last weekend's on a highway toll plaza in which two trucks were set on fire.

"We've decided to invoke the anti-terror Law to go after these groups of people who are set on perpetrating crimes, disorder and unrest in a region seeking peace and harmony," he said.

"We won't allow or tolerate these groups carrying out these types of actions again," he added.

The Mapuche community is suspected of being behind the recent attacks after pamphlets alluding to its cause were found near the truck fires, local officials said.

The Mapuches form Chile's largest indigenous group, accounting for six percent of the country's population of 16 million.

Pinochet's 1973-1990 military regime is blamed for some 3000 deaths and disappearances in a "dirty war" against the left.

Pinochet died in December 2006 at a military hospital in Santiago, at the age of 91, after evading repeated attempts to bring him to trial for human rights abuses committed during his rule.