SANTIAGO, Chile (AP) — Chile police said Thursday they arrested 264 people and that 42 officers were wounded during a long night of violence on the anniversary of Chile's 1973 coup.

Police say six officers were seriously injured late Wednesday when hooded vandals hurled acid at them. Gen. Rodolfo Pacheco, one of the Chilean capital's top police chiefs, was taken by helicopter to a hospital after being struck in the head by an unlit gasoline bomb. Three public buses also were set on fire to make barricades in the streets of Santiago.

President Sebastian Pinera submitted a bill to Congress earlier this year that stiffens penalties for those who insult or physically harm police and makes it a crime to attack police headquarters or vehicles. He visited the injured officers Thursday and asked the public to help identify the attackers.

"Last night was a violent night, but it could have been much more violent if it hadn't been for the efficient response of police," Pinera told reporters. "Our conclusion is that the violence was committed by organized groups joined by the usual delinquents."

Chilean protests are often infiltrated by violent anarchist groups and end with clashes between police and hooded vandals who throw rocks, firebombs and even acid.

Pinera recently said that in the last two years, "more than 700 police officers have been injured by the cowardly acts of hooded vandals, including recent victims who were burned with acid or Molotov bombs."

The latest streak of violence comes on the 40th anniversary of the Sept. 11, 1973, coup that began Gen. Augusto Pinochet's brutal dictatorship. The government estimates 3,095 were killed during Pinochet's rule, including about 1,200 who were forcibly disappeared.

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Luis Andres Henao on Twitter: https://twitter.com/LuisAndresHenao