SANTIAGO, March 26 (Reuters) - A bomb exploded at a bank in the Chilean capital on Wednesday, the second attack in 10 days, and authorities blamed anarchists, who hold protests at this time every year.A fire extinguisher containing a homemade explosive charge detonated at the door of a branch of state-run BancoEstado in west Santiago. No one was injured, but a door and windows were damaged."We believe (those responsible) are anarchists," a source at the state prosecutor's office said, asking not to be named. "(The bombs) are part of the propaganda of these groups."On Saturday, anarchists are expected to mark the anniversary of the deaths of two militant brothers during Augusto Pinochet's iron-fisted 1973-1990 rule.There have been numerous bomb threats leading up to Saturday's anniversary, known as the "Day of the Young Combatant," which has become a lightning rod for protests by anti-establishment groups and radicals.Shortly after Wednesday's blast, police evacuated students from a school in the capital after a bomb threat.Last year, groups of students wearing balaclavas clashed with police in the capital and other cities, some throwing stones and molotov cocktails at police, who retaliated with tear gas and water cannon.At least 12 police were wounded in the clashes, and many shops and businesses closed down for the day. Several explosive devices detonated, but no one was injured.Chile's government has vowed to clamp down on radical groups who set off bombs, and extra police will patrol the streets of Santiago on Saturday."We are always on guard, but we won't get caught up in their game," government spokesman Francisco Vidal told reporters. (Reporting by Simon Gardner and Antonio de la Jara)
The protesters tried to march in front of the presidential palace, but it was cordoned off. 
Around 240 demonstrators in the Chilean capital of Santiago were detained Friday after anti-government protests held against the country's education system and increasingly free market policies.

The annual protests, organized by the Revolutionary Left Movement, were held on the eve of the Day of the Youth Combatant. The day commemorates the deaths of Eduardo and Rafael Vergara, brothers who were assassinated on March 29, 1985 under the dictatorship of Augusto Pinochet.

The protesters, many of whom were students, reportedly threw rocks into Santiago's main street, prompting squads of riot police to spray tear gas into the crowds. Other protesters marched towards the presidential palace, but it was cordoned off and heavily guarded. Most of the 240 who were detained are expected to be released after their identities are confirmed.

In between skirmishes with police, some protesters handed out flyers explaining their views. They say the government has manipulated the education system to favor the rich. "We think this neo-liberal education system that the government has introduced should be stopped," said Saray Acevedo of the National Popular Coordinator of Students.

President Michelle Bachelet condemned the protests. "If one wants to pay homage to the tremendous tragedy of the Vergara brothers, during a period when Chile was not democratic, the right thing to do is guarantee that democracy means being able to express yourself but without violence," she said. "Democracy in Chile is solid and there is no justification for violence," Bachelet added.

Other Chileans who didn't take part in the demonstrations agree with some of the protesters' views. "There are so many problems," said Rodrigo Núñez, 39. "It is true education is expensive and marginalizes the poor. The cost of living is high. Electricity and gas prices are up. Look at how they protest in Argentina! I voted for this government and feel conned."

2 days before Friday's protests, a bomb exploded in a Santiago bank. Police blamed the attack on "anarchists", and they believe it was connected to the annual protests.

Additional protests are planned for Saturday, when the Day of the Youth Combatant will be formally recognized.