Santiago police sprayed water cannon and tear gas on Tuesday to disperse protesters supporting a nationwide strike by high-school students to demand changes to Chile's education law, including a federal takeover to reduce inequality between rich and poor schools, as protests across the country resulted in 725 arrests and left 14 people injured.
Teachers and university students joined the demonstrations, which organizers said drew more than a million people, giving President Michelle Bachelet the first major test of her new administration.
The government said the injured included two police officers and three reporters.
The massive protest forced Bachelet to convene an emergency meeting with some Cabinet members at the presidential palace.
Protest leaders had urged students to remain inside their schools without attending classes, a decision supported by many teachers, parents and politicians. But shortly after noon, hundreds of students attempted to march downtown.
Masked young men threw rocks and erected barricades at some key intersections, while police responded with water cannons and tear gas. The clashes lasted until dusk, as police dispersed demonstrators who repeatedly regrouped.
Authorities and leaders of the students' movement said the masked men were infiltrators, who succeeded in blocking traffic at Alameda, Santiago's main avenue, for more than four hours.
The protests spread to several other cities, but by nightfall calm had been restored, Deputy Interior Minister Felipe Harboe said.
Nearly 600,000 public high school students joined the stoppage, which also won support from students at many private schools, including the one attended by Bachelet's younger daughter.
The strength of the students movement has surprised many in Chile, and is seen as the first major conflict faced by the government of Socialist Bachelet, inaugurated on March 11.
By the end of the day on Tuesday, talks between the government and students had progressed, Education Minister Martin Zilic said. He said talks would resume yesterday, but did not elaborate.
Several students confirmed the talks.
The students began with modest demands such as reduced fares on public transportation and the elimination of a US$38 fee for an exit exam that lets them apply for college.
They demanded that three hours recently added to the school day be dedicated to sports, the arts or other activities.
The movement spread from Santiago to the provinces and the demands expanded to include deep reforms of the country's education law, which was issued by former dictator General Augusto Pinochet one day before he left office in 1990.
The law assigns responsibility for public education to municipalities, which critics say breeds inequality because of regional differences in available resources.
A monthly government subsidy of US$57 per student does not compensate, they say.
"We want the state to be the only guarantor and administrator of public education," said Javier Romero, a leader of the movement. "Only that would ensure equality."
Former education minister Jose Joaquin Brunner said the poorest schools allocate an estimated US$73 a month per student, compared with more than US$385 at the richest.
The law also allows the virtually uncontrolled creation of private schools that are entitled to government subsidies.