A strong 6.0-magnitude earthquake has shaken Chile, rattling buildings in the capital while a big anti-government demonstration was under way.

The quake struck at 6:53pm with its epicenter near the northern town of Illapel, the US Geological Survey said.

A strong and prolonged shaking was felt in the capital.

Chile's National Seismological Center measured the quake at magnitude 6.1, revising down an earlier estimate of 6.3.

There were no immediate reports of damage or casualties.

"There have been no reports of damage to people, disruption of basic services or infrastructure," the National Emergency Office said.

The Army Hydrographic and Oceanographic Service said the quake was unlikely to cause a tsunami on Chile's Pacific coast.

When the quake hit, police in Santiago were dispersing protesters at the start of the third week of anti-austerity protests targeting the conservative government.

Clashes between demonstrators and police have left 20 people dead

Nobel Peace winner confronts Chile over police abuses

Earlier, a Nobel Peace laureate added her voice to calls for Chile to stop police violence against protesters during recent weeks of deadly anti-government unrest.

Protests against economic hardship have erupted into vandalism, looting and clashes between demonstrators and police, leaving 20 dead.

Prosecutors say five of those people died at the hands of state agents. A UN human rights mission is investigating allegations of police brutality.

Rigoberta Menchu of Guatemala

The 1992 Nobel Peace Laureate, Rigoberta Menchu of Guatemala, led other activists in delivering a letter at the presidential palace urging an end to what they called "serious and systematic" abuses.

They called on Chile's President Sebastian Pinera to "immediately halt the violence" by security forces.

Chile's independent National Human Rights Institute says it has brought legal action over 179 cases including alleged murders, sexual violence and torture by the military police.

Chile's president Sebastian Pinera

The institute's director, Sergio Micco, denied that the abuses constituted a systematic government policy, however.

The institute says 1,574 people have been hurt in the unrest.

"Terrible acts of repression have been carried out by members of the security forces and other state agents," said the letter, read out by activist Guillermo Whpei.

Ms Menchu backed protesters' calls for constitutional reform in Chile. The current constitution dates back to the 1973-1990 dictatorship of Augusto Pinochet.

Read more:
Chile president announces social measures to stem street violence
Spain to host COP25 climate talks after Chile withdraws