Eleven people died after looters torched a garment factory near Chile's capital Santiago, bringing the death toll in violent protests to at least seven.
After an emergency meeting late on Sunday, President Sebastian Pinera defended his decision to call a state of emergency and deploy troops onto the streets for the first time since Augusto Pinochet's military dictatorship between 1973 and 1990.
"Democracy not only has the right, it has the obligation to defend itself using all the instruments that democracy itself provides, and the rule of law to combat those who want to destroy it," Pinera said in a late-night televised address at army headquarters in Santiago.
"We are at war against a powerful enemy, who is willing to use violence without any limits."
Earlier on Sunday, police and the military fired tear gas and used water cannon against protesters in the city as clashes over price hikes and social inequality raged through a third day, forcing the government to extend the curfew.
Almost all public transport was paralysed in Santiago, with shops shuttered and many flights cancelled at the international airport, leaving thousands of people stranded and unable to leave due to the curfew, which was also extended for a second night.
The dusk-to-dawn curfew goes into effect from 7pm (22:00 GMT), after which people should "be calm and all in their homes," said top defence official General Javier Iturriaga.
Iturriaga was appointed head of national defence by Pinera on Friday as he declared a state of emergency over the unrest.
Interior and Security Minister Andres Chadwick also said new decrees were being drawn up for Antofagasta in the north, Valdivia in the south, and other cities such as Valparaiso, Temuco and Punta Arenas.
The military and police used tear gas and water cannon against protesters and a curfew was imposed in major cities.
A state of emergency already in place in Santiago is to be extended to cities in the country's north and south.
The unrest, sparked by a now suspended metro fare hike, has widened to reflect anger over living costs and inequality.
There is set to be major disruption on Monday with many banks, schools and shops expected to remain closed.
Firefighters say they found five bodies inside the garment factory burned by rioters in a suburb of Santiago. Earlier reports suggested three others had died in a supermarket fire in Santiago on Saturday.
Interior Minister Andrés Chadwick said at least seven people had died in incidents related to the protests, without giving details.