Police fired tear gas against protesters denouncing the announcement by Chile's ruling junta that the sole candidate in an October presidential plebiscite will be Gen. Augusto Pinochet, who took power nearly 15 years ago in a coup.

A city-operated emergency medical center said a 15-year-old boy at one of the protests was killed by gunfire, which witnesses said came from a passing car. Police said 21 people were injured and 364 detained Tuesday during anti-Pinochet protests around the country.Protesters congregated on street corners in downtown Santiago and chanted until police arrived and dispersed them with torrents of water and clouds of tear gas. They then ran elsewhere and resumed their anti-government chanting.

Bonfires blocked several suburban streets Tuesday night after the junta's expected announcement that Pinochet would be the candidate in an Oct. 5 plebiscite. A "Yes" vote will give him eight more years as president, while a "No" vote is call for an open election in about a year.

Pinochet, 72, who seized power in the 1973 coup in which socialist President Salvador Allende died, appeared on a balcony of the presidential palace after the nomination was announced, waving to thousands of supporters who gathered below.

A huge fireworks display lighted the square in front of the building as the crowd shouted, "Long live Pinochet!"

At the same time, a specially equipped black-and-white pickup truck, called a "skunk" by residents, sprayed protesters on the other side of the palace.

"In the years that I have left, if I am named president of the republic by the people, I will entirely dedicate myself to the service of my people," Pinochet told the crowd beneath the balcony.

Ricardo Lagos, a director of the opposition coalition called the Command for the No, said, "The opera has finished. The dictator has imposed his will and he is ready to continue dominating the people until the end of the 20th century."

The opposition said thousands of people banged pots and pans to protest the nomination.

Radio reports said demonstrations erupted in other Chilean cities, including Valparaiso, on the Pacific coast 70 miles west of Santiago, where police met university students trying to march downtown.

There had been speculation, based on the comments of other members of the junta, that Pinochet would step down as head of the armed forces. But he appeared throughout the day in his uniform and no mention was made of his resignation.

Pinochet went to a chapel in the presidential palace and prayed after the junta's noon meeting, a presidential spokesman said.

Immediately after the announcement, Pinochet, in a televised speech to the nation, said the 1973 coup was necessary to rid Chile of the Marxist Allende government.

At least three different groups of several thousand anti-Pinochet protesters were met by police in riot gear who used tear gas and water cannons to disperse them during the junta's meeting.