Commuters enraged by delays in an evening train service on Tuesday set fire to parts of a railroad station, looted nearby shops and clashed with riot police.
Police fired rubber bullets and tear gas as rioters pelted them with rocks. The fighting at Buenos Aires' Constitucion station spilled into a nearby street as demonstrators shattered windows, set fire to a ticket sales area, looted shops and ripped pay phones from walls.
Hundreds of passengers fled the fighting inside train station, one of the busiest in South America with an estimated 300,000 commuters daily.
Twelve police officers were injured by flying rocks, mostly with cuts and bruises to the head and chest, and nine people were also treated at the scene for smoke inhalation, said Alberto Crescenti, a spokesman for emergency medical workers.
Police Commissioner Ricardo Falana reported 16 arrests, including two minors.
He said about 100 police were needed to quell the rioters, who he said threw a "hail of rocks" at officers.
During the disturbances, a motorcycle was set ablaze and angry youths used metal poles to try to break down tall wooden doors to a security office in the station. Firefighters quickly put out small fires in trash cans and the ticket area. Shattered glass, bricks and sticks littered the hall afterward.
The fighting threw evening rush hour into chaos, forcing the cancellation of all train services on Tuesday evening.
Fernando Jantus, a spokesman for the Metropolitano train concession, said service was interrupted at the evening rush hour because a train broke down on a key track just outside the station, blocking other trains from leaving the station.
"The problem happened at the worst moment," he said, noting the rioting began in the peak evening rush around 6:30pm.
Passengers have long complained about poor commuter rail services on lines leading from Constitucion station in downtown Buenos Aires to poor southern suburbs of the Argentine capital.
Tuesday's riot was the second major outbreak of violence at the station since passengers angry over the cancellation of train services last September set three train cars ablaze.
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