SANTIAGO, Chile (AP) — Armed assailants ambushed and killed three law enforcement officers in southern Chile on Saturday before setting their car on fire, authorities said, the latest attack on police to revive security concerns in the South American country.

It remains unclear who carried out the assault on Chile’s national police force in the Biobío region some 400 kilometers (about 250 miles) south of Santiago, the capital. But a long-simmering conflict between the Mapuche indigenous community and landowners and forestry companies in Biobío and Chile’s Araucanía region farther south has intensified in recent years. That has prompted the government to impose a state of emergency and deploy the military to provide security.

“There will be no impunity,” Chilean President Gabriel Boric said, declaring three days of national mourning on Saturday, after firefighters dousing the burning police car made the grisly discovery.