Riots broke out in an Argentine suburb as a protest against the suspension of a train service turned violent.
Angry passengers and masked demonstrators fought street battles with police.
At least 15 train carriages and police cars were torched. Nearby shops also caught fire.
More than 80 people were arrested during the five-hour rioting at Haedo station, 15km west of Buenos Aires.
The incident left at least 20 people injured. Two train carriages were completely destroyed.
It is one of the worst incidents seen in Argentina since the country's economic collapse four years ago.
The clashes come as Argentina prepares for the Americas summit, which will be attended by President Bush and other regional leaders.