Chilean President Sebastian Pinera on Sunday vowed “no impunity” for security forces that used excessive force and violated the rights of protesters during weeks of violent riots over economic policies and social injustice that have left more than 20 dead.

Public prosecutors in Chile are investigating more than 1,000 cases of alleged abuses - ranging from torture to sexual violence - by the police and military.

“Despite our firm commitment and precautions ... to protect human rights, in some cases protocols were not adhered to, there was excessive use of force and abuses and crimes were committed,” Pinera said in a televised speech Sunday night.

“There will be no impunity,” he added.

Protests have rocked Santiago for a month in the biggest crisis to hit the South American nation since its return to democracy in 1990. Weeks of unrest have knee-capped the economy, prompting increasingly grim forecasts for growth and unemployment.

Pinera´s government has promised a raft of reforms to quell protesters' demands, from beefing up the minimum wage to topping off pensions.

Chilean lawmakers on Friday also announced a deal to hold a referendum in April on replacing the country's dictatorship-era constitution, a major concession to protesters who say it is rigged against the poor.