Tens of thousands of protesters swarmed Chile's capital Wednesday, setting up fiery barricades and clashing with riot police as an apology and promises of economic reform from President Sebastián Piñera failed to calm the unrest that has led to at least 18 deaths.

The movement started with anger at a small rise in subway fares, but blew up last week into protests demanding improvements in education, health care and wages in one of Latin America's wealthiest, but most unequal nations.

Many protesters in Santiago waved the national flag and shouted "Chile has woken up!"

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Police responded to stone-throwing demonstrators by spraying water cannons and firing rubber bullets and tear gas. Similar scenes were repeated in towns and cities all along the long, narrow South American country of 18 million people.

Approximately 20,000 soldiers are patrolling the streets. Nearly 200 people have been injured, and some 5,000 have been arrested.

Human rights groups expressed concerns about how security forces have handled the protests after the government ordered a military curfew. It was the first such curfew — other than for natural disasters — imposed since Chile returned to democracy in 1990 following a bloody 17-year dictatorship.

A demonstrator throws a stone at a police vehicle during the sixth day of protests in Chile Marcelo Hernandez via Getty Images

"We're worried," José Miguel Vivanco, Americas director at Human Rights Watch, told The Associated Press. "The images that we've received from credible sources, trustworthy sources, show that there has been an excess of force both by police as well as some soldiers."

The Inter-American Commission on Human Rights also criticized what it said is excessive use of force by security forces as well as the "violent acts committed by civilians" in the protests. It called for dialogue to hear "people's legitimate demands."

Millions of students were still unable to attend classes, several subway stations were shut, and long lines wound from gas stations and supermarkets after many stores were torched or destroyed.

Most of the protests have been peaceful, with demonstrators of all ages banging pots to demand reforms. But the unrest also involved riots, arson and looting that have wracked Chile for six days, nearly paralyzing a country long seen as one of the region's most stable.

"Today we're protesting all of our discontent against these politicians who have been fooling us. The raise in the subway fare was just the straw that broke the camel's back," Italo Tarsetti told The Associated Press.

Many supermarkets have been looted as Chileans protest inequality in the nation's capital Marcelo Hernandez via Getty Images

Faced with the mounting unrest, Piñera on Tuesday night announced economic reforms that include increases in the minimum wage and the lowest state pensions. But many said the 69-year-old billionaire businessman reacted too late, and the announcement failed to calm anger in the streets.

"These measures are absurd. It's handing out crumbs to the people," Magdalena Bravo, a demonstrator who said she had lost her job as a school teacher, told The Associated Press.

The economic agenda Piñera announced Tuesday night calls for increasing the lowest monthly pensions from $151 to $181, raising the monthly minimum wage from $413 to $481 and rescinding a 92% rise in electricity rates scheduled to take effect next month. It would also increase taxes for anyone earning more than $11,000 a month.

"Piñera's more conciliatory tone is a step in the right direction, but the proposal on its own is unlikely to suffice," Jenny Pribble, associate professor of political science at the University of Richmond, told The Associated Press.

Thousands of Chileans march to protest inequality Marcelo Hernandez via Getty Images

Pribble said that while it would boost pensions and set a minimum income, the package doesn't address the structure of the country's health and pension systems.

"This is a point of concern for the protesters and the president must signal that he is open to a social dialogue that would, at a minimum, debate the possibility of abandoning the privatized logic," she said.