Troops have been patrolling the streets of the Chilean capital Santiago after President Sebastian Pinera evoked a state of emergency amid a surge in violent protests over a hike in public transport fares, the military has confirmed.

Hundreds of thousands of commuters were trapped on their way home from work in Santiago on Friday after high school students flooded subway stations as part of protests against a fare hike.

The capital city descended into chaos amid riots that left a downtown building engulfed in flames and its metro system shuttered.

Subway services in Santiago were suspended after activists jumped turnstiles, dodged fares and vandalised stations as part of demonstrations which quickly spread throughout the city of six million.

By nightfall on Friday, students had set up barricades and started fires at the entrances to subway stations.

Police told Reuters that on Friday alone, 156 police officers had been injured, including five seriously. Forty-nine police cars were damaged, 41 metro stations vandalised and 308 people were detained.

Javier Iturriaga del Campo, the general designated in charge by Mr Pinera, told a news conference at Santiago‘s Moneda presidential palace in the early hours of Saturday that his troops would focus their patrols on “the most conflict-hit areas” but would impose no curfew “for now.”

“The recommendation for people is that they can go home to be with their families and be calm,” he said.

“We are assuming control, deploying our forces in a way that we can prevent continuing acts of vandalism and having a better sense in the morning of what is happening.”

Mr Pinera said he would invoke a special state security law to prosecute the “criminals” responsible for the city-wide damage, while at the same time saying he sympathised with those impacted by the rate hikes.

“In the coming days, our government will call for a dialogue ... to alleviate the suffering of those affected by the increase in fares,” the centre-right leader said in the broadcast address.

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Protests against Chilean President Sebastian Pinera's government were triggered months ago after Pinera proposed changes to the country's pension system REUTERS Riots flare across Chile as anti-government protests continue Demonstrators clash with security forces REUTERS Riots flare across Chile as anti-government protests continue Demonstrators protest in Plaza Italia in Santiago EPA Riots flare across Chile as anti-government protests continue A riot police water truck is hit by a molotov bomb REUTERS Riots flare across Chile as anti-government protests continue A demonstrator throws stones REUTERS Riots flare across Chile as anti-government protests continue A demonstrator blows fire from his mouth as he clashes with riot police REUTERS Riots flare across Chile as anti-government protests continue A demonstrator kicks back a tear gas canister REUTERS Riots flare across Chile as anti-government protests continue Riot police are reached by a petrol bomb AFP via Getty Images Riots flare across Chile as anti-government protests continue A demonstrator uses a tennis racket to throw a tear gas canister back at riot police AFP via Getty Images Riots flare across Chile as anti-government protests continue SANTIAGO, CHILE - JANUARY 17: A Chilean riot police officer throws a gas pump against demonstrators during a protest against President SebastiÃ¡n PiÃ±era at Plaza Italia on January 17, 2020 in Santiago, Chile. Protests and social unrest arose on October 18 after a subway fare increase which developed in a social movement demanding improvements in basic services, fair prices and benefits including pensions, public health and education. (Photo by Marcelo Hernandez/Getty Images) Marcelo Hernandez Getty Images Riots flare across Chile as anti-government protests continue Demonstrators are sprayed by riot police with a water cannon REUTERS Riots flare across Chile as anti-government protests continue An anti-government demonstrator covers his mouth and nose during a protest with a sticker on his head that reads in Spanish: "Dignity," AP Riots flare across Chile as anti-government protests continue A demonstrator next to a burning barricade REUTERS Riots flare across Chile as anti-government protests continue A demonstrator with a placard that reads "United until the Victory" REUTERS Riots flare across Chile as anti-government protests continue Demonstrators clash with riot police during a protest in Santiago AFP via Getty Images Riots flare across Chile as anti-government protests continue Demonstrators clash with security forces REUTERS Riots flare across Chile as anti-government protests continue A police water cannon sprays water over anti-government demonstrators AP Riots flare across Chile as anti-government protests continue A demonstrator throws a tear gas canister back at riot police AFP via Getty Images Riots flare across Chile as anti-government protests continue A demonstrator gestures near a burning vehicle REUTERS Riots flare across Chile as anti-government protests continue Matias Orellana, who lost his right eye due to impact from a tear gas canister shot by security forces, waves to demonstrators gathered to support him outside a hospital REUTERS Riots flare across Chile as anti-government protests continue Demonstrators take part in a protest against Chile's government in Valparaiso, Chile December 30, 2019. REUTERS/Rodrigo Garrido RODRIGO GARRIDO REUTERS Riots flare across Chile as anti-government protests continue Riot police officer shots a tear gas canister Getty Images Riots flare across Chile as anti-government protests continue Thousands of Chileans protest against the government of President Sebastian Pinera Getty Images Riots flare across Chile as anti-government protests continue A demonstrator throws items at an armoured vehicle REUTERS Riots flare across Chile as anti-government protests continue Demonstrators point green laser lights at police during protests in Santiago, Chile Getty Images Riots flare across Chile as anti-government protests continue Demonstrators point green laser lights to riot police during a protest Getty Images Riots flare across Chile as anti-government protests continue Demonstrators point green laser lights at riot police officers Getty Images Riots flare across Chile as anti-government protests continue Demonstrators use laser beams during an anti-goverment protest in Santiago, Chile on 12 November. REUTERS Riots flare across Chile as anti-government protests continue Observers compared the use of lasers to futuristic warfare or a dance club party AFP via Getty Images Riots flare across Chile as anti-government protests continue Anti-government protesters clash with riot police in Renaca on Chile's coast AFP/Getty Riots flare across Chile as anti-government protests continue Demonstrators burn piles of furniture during a protest against Chile's government in Vina del Mar, on the country's northern coast Reuters Riots flare across Chile as anti-government protests continue Demonstrators clash with riot police during a protest on 12 October AFP/Getty Riots flare across Chile as anti-government protests continue A demonstrator is arrested by Chilean riot police during a protest in downtown Santiago on 12 October AFP/Getty Riots flare across Chile as anti-government protests continue A demonstrator waves a Chilean flag as he is fired upon by water cannons during clashes with riot police during anti-government protests in Concepcion on 4 November Reuters Riots flare across Chile as anti-government protests continue Demonstrators throw stones during a protest against Chile's government in Concepcion, near the country's coast on 7 November Reuters Riots flare across Chile as anti-government protests continue A woman walks with her children amid anti-government protests in Concepcion, on Chile's coast on 7 November Reuters Riots flare across Chile as anti-government protests continue Demonstrators clash with riot police during a protest in downtown Santiago on 12 October AFP/Getty Riots flare across Chile as anti-government protests continue Subway services in Santiago were suspended after activists jumped turnstiles, dodged fares and vandalised stations AFP/Getty Riots flare across Chile as anti-government protests continue Demonstrators run away from tear gas during clashes with riot police at the Bellas Artes metro station AFP/Getty Riots flare across Chile as anti-government protests continue School and university students joined a mass fare-dodging protest in Santiago's metro AFP/Getty Riots flare across Chile as anti-government protests continue A riot police throws a tear gas canister to demonstrators during clashes AFP/Getty Riots flare across Chile as anti-government protests continue Riot police stand next to a burning barricade following a mass fare-dodging protest in downtown Santiago AFP/Getty Riots flare across Chile as anti-government protests continue Chile's President Sebastian Pinera declared a state of emergency in October AFP/Getty Riots flare across Chile as anti-government protests continue A protester kicks back a tear gas canister during clashes with riot polic AFP/Getty Riots flare across Chile as anti-government protests continue Demonstrators clash with riot police following a mass fare-dodging protest AFP/Getty

Television images showed students and others attacking police vehicles, throwing stones and burning at least one bus, along with scenes of destruction and shattered glass inside various metro stations.

Police who had been trying to break up the protests with tear gas withdrew from some subway stations.

The president allowed authorities to restrict people’s rights to assembly and movement. The move was aimed at guaranteeing “the security of residents, protecting goods and the rights of each one of our compatriots who have seen complications from the actions of true criminals”, Mr Pinera said in a speech from the government palace.

Transportation minister Gloria Hutt, who earlier rejected lowering fares, said: “It’s possible that during the next week the functioning (of the subway system) returns in a gradual fashion.”

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The government filed a complaint under the state security law against people who damage the subway system or prevent its normal operation, according to interior minister Andres Chadwick. The law carries prison sentences of three to five years for offenders.

The protest by students began on Monday when hundreds of young people mobbed several stations in Santiago, jumping over or dipping under turnstiles to protest a 16 per cent increase in subway fares from about one dollar to one dollar and 16 cents.

Chile does not produce its own oil and must import its fuel, leading to high prices for petrol, electricity and elevated public transportation costs.

By the end of the week, the protests had turned violent with students breaking gates, shattering glass and throwing debris onto the electrified rails. A train driver was injured by broken glass.

The protests have divided Santiago residents between those who feel the protests are justified and those furious at the long commuting delays.

“It’s unacceptable that because of schoolchildren we can’t return to our homes,” said bank worker Daniel Fuentealba.

Eric Campos, leader of the subway workers’ union, reported that at least 16 employees had been injured and called for the closure of the entire subway system.

Faced with the protests and mass fare evasion, the Metro closed three of its six lines on Friday afternoon before shutting them all at nightfall.

The National Co-ordinator of Secondary Students, one of two groups representing high school students, called for the protest to continue.

Metro officials say the fare price was raised because of a devaluation of the currency, rising fuel costs and the need for maintenance.