Pinera said he hoped to turn recent violent protests into an "opportunity" for Chile, to "make up for lost time, pick up the pace and take concrete and urgent steps" to resolve inequality that has sent tens of thousands into the streets to demand an economic overhaul and, in some cases, his removal.

The 69-year-old centre-right president asked for forgiveness for successive governments on both left and right that failed to act sooner to stem deep inequalities in Latin America's fifth-largest economy.

"I recognise and apologise for this lack of vision."

The pledges came after a tumultuous start to the week for Pinera, who was widely criticised for saying on Monday that Chile was "at war" with violent protesters, as thousands of people held successive, peaceful demonstrations demanding an end to low wages and a high cost of living.

At least 15 people have died in protests that started over a hike in public transport costs, prompting a weekend of riots, arson attacks and looting of businesses and the declaration of a state of emergency by Pinera over a large swath of Chile.

Further protests are expected on Wednesday, along with a general strike called in solidarity with the demonstrations that will include the union of top copper miner Codelco, opening a potentially new, damaging front in the crisis for the world's top producer of the red metal.

On Tuesday, Pinera held a roundtable for politicians of all colours to forge a new "social contract" to help Chile's poor and middle-classes, who find themselves battling economic pressures.

In a speech delivered from La Moneda presidential palace he pledged to up the minimum pension by 20 per cent and increase the state's contribution for the middle classes and women, fast-track a law to introduce a state critical illness cover, cut prices of medicines for the poor, and guarantee a minimum wage of $US480 ($A700) a month.

The state would intervene to stabilise an electricity utility hike, and rebalance disparities in municipal budgets to support poorer areas, he said.

He recognised the potentially "enormous" cost of the new measures, and also announced a new tax bracket of 40 per cent for those earning more than $US11,000 a month, as well as looking to cut the wages of lawmakers and public officials.

Pinera's offer represented "an enormous victory for our citizens," said socialist Oscar Landerretche, a former chairman of state copper miner Codelco and touted presidential candidate for 2021.

On Tuesday, prosecutors confirmed the death toll in the unrest had risen to 15, adding that 5400 people had been detained by security forces.

There were further marches around the country, triggering more clashes with police and soldiers. In a poor area of Santiago, protesters were pictured hijacking a city bus to ram into a department store.

The military general in charge of security in Santiago said he was aware of videos circulating on social media suggesting brutality by police or the military in tackling protesters and vandals.

"We are investigating every one of these situations," General Javier Iturriaga told reporters. "We're not going to hide anything."

Interior ministry sub-secretary Rodrigo Ubilla said 11 people had died in arson attempts, looting and rioting in Santiago, while two people had died of gunshot wounds.

Australian Associated Press