The ban was imposed to avoid trouble during renovation work taking place at the symbolic Taksim square, a traditional rallying point.
Protesters threw stones at the police who tried to prevent the protest in the Besiktas neighborhood of Istanbul, which is about two kilometers (a mile) from Taksim square.
“Death to fascism. Long live May 1,” shouted the protesters who were rallying to calls from leftist parties and unions.
Clashes erupted in three neighborhoods leading to Taksim Square where the authorities had blocked off the streets to prevent protesters from reaching it.
The Istanbul office of Prime Minister Recep Tayyip Erdogan, located in Besiktas, were barricaded and defended by dozens of policemen backed by anti-riot armored vehicles.
A group of 30 feminists, waving violet flags and shouting “all together against fascism”, was pushed back by police firing tear gas.
Thousands of police were mobilized for the day.
Television stations said Labor Day was celebrated without incident in two other parts of the massive Turkish city.
The Turkish government decided to ban May Day gatherings on Taksim Square, saying that because of renovations begun in November, security could not be assured for the tens of thousands of demonstrators expected.
But the leftist Disk union vowed to ignore the ban.