Students and trade unionists led marches through Santiago on Wednesday in the first formally organized demonstration against social inequality since Chilean President Sebastian Pinera pledged social reforms to try to quell days of rioting.

Thousands of striking workers, including healthcare workers and teachers, sang and carried banners in the capital and other cities. The largely peaceful marches were monitored by police and soldiers.

The gatherings dovetailed four days of protests, arson attacks and looting which has seen more than 6,000 people detained and at least 15 people killed. Thousands of Chileans defied a state of emergency and military curfews.

Trade unions and social organizations wanted a voice in the rollout of a social reform plan announced by Pinera on Tuesday night, said José Pérez Debelli, president of the National Grouping of Fiscal Employees (ANEF), one of the unions that called the strike.

"We must carry the voice of those who are on the street, to channel anger and discontent over the inequality of our country," he said.

The Copper Workers Federation (FTC), which includes unionized workers from each division of state miner Codelco, the world's top copper producer, agreed late on Tuesday to join the general, nationwide strike on Wednesday.

Codelco said one of its mines was shut and operations at a smelter drastically reduced.

Six of Codelco's eight divisions were carrying on with the "majority of their operations," the company said in a statement.

Copper producer Antofagasta Plc said on Wednesday protests in Chile could cut its production by about 5,000 tons, equivalent to less than three percent of third quarter output, because of delays in supplies and travel disruptions for workers.

Jimena Blanco, Head of Latin America research at consultancy Verisk Maplecroft, said it was "a matter of time" before the knock-on effects along the supply chain had a negative impact on the mining industry.

"For example, yesterday's strike by the port workers' union affected 20 of the country's maritime facilities, including key mining export ones in Antofagasta and Iquique," she said.

In his announcement, Pinera said he hoped to turn the violent protests into an "opportunity" for Chile.

Pinera's proposed reforms include a guaranteed minimum wage, a hike in the state pension and the stabilization of electricity costs.