A video showing a shocking incident of police brutality is circulating of social media. According to various Chilean media, a police officer used a 13-year-old boy as a human shield while firing tear gas at protesters.

It remains unclear where exactly the incident took place. According to some sources, it occurred in Providencia, a district in Chile's capital city, Santiago. Other online media report that it took place in Rancagua, more than 80km south of the capital.

Chile's ombudsman for children, Patricia Muñoz, took to Twitter to ask citizens to provide information about the victim and his family.

Chile president fends off police-abuse claims

Chile's president said Wednesday his government had "nothing to hide" concerning allegations that police killed, tortured and sexually assaulted civilians during deadly protests against him.

Prosecutors say five of the 20 deaths recorded in the protests against high living costs were suspected to have been at the hands of security forces.

"We have been totally transparent about the figures because we have nothing to hide," President Sebastian Pinera said in a speech on Wednesday.

Clashes between protesters and police have turned parts of the capital Santiago into a battleground over recent nights.

On Wednesday, protesters called on demonstrators to expand their rallies to rich districts so far untouched by the wave of demonstrations, centering on a major shopping center.

The Costanera Center is South America's biggest shopping center and a symbol of the economic expansion that had made Chile one the region's most stable countries until the latest unrest.

Other messages called on protesters to rally in the upmarket Vitacura district at the United Nations Economic Commission for Latin America and the Caribbean.

On Tuesday, riot cops firing shot pellets injured two students among a group trying to overrun a public high school in Santiago, police said. The students were treated at a hospital and released.

The crisis has forced the government to cancel separate international economic and climate summits as well as a major international football match, the Copa Libertadores final.

A UN human rights mission is investigating allegations of police brutality during the unrest.

Demonstrators have clashed with riot police / © AFP

The Washington-based Inter-American Commission on Human Rights on Wednesday also asked Pinera's authorization to send a mission to Chile at the request of human rights groups.

Chile's independent National Human Rights Institute says it has brought legal action over 181 cases including alleged murders, sexual violence and torture by the military police.

Pinera said state agents who committed abuses would be punished just as severely as those who carried out vandalism or violence in the protests.

He has reshuffled his government and announced a series of measures aimed at placating the protesters.

In the latest of these, on Wednesday he signed a law guaranteeing a minimum monthly wage of some $467.

But protesters have continued demanding that the right-wing billionaire president step down.

Pinera said in a BBC interview broadcast Tuesday that he would not resign over the protests.