“Having monitored the crisis in Chile since it began, I have decided to send a verification mission to examine the allegations of human rights violations,” the head of the UN Human Rights Council and former Chilean president, Michelle Bachelet, said in a tweet.

Eighteen people including a four-year-old child have been killed since the violence escalated nearly a week ago over a now-scrapped hike in metro fares.

The unrest — widespread looting, arson and clashes with security forces deployed on the streets — is the worst to hit Chile since it returned to democracy after the 1973-1990 right-wing dictatorship.

Social measures announced by President Sebastian Pinera this week have failed to stem the unrest.

Thousands of people joined a general strike in the capital Santiago and other cities on Wednesday, with police using water cannons to disperse the demonstrators.

The strike was set to continue on Thursday.

Bachelet said on Monday that she was “deeply disturbed and saddened to see violence, destruction, deaths and injuries in Chile”.