More than 100,000 Turkish workers thronged a central Istanbul square on Saturday for May Day celebrations, held there for the first time since the late 1970s, when unknown gunmen massacred dozens of people.
Groups from six union confederations and political parties poured into Taksim Square, singing and chanting slogans such as "long live May Day." The crowds waved red-and-white Turkish flags and party banners.
More than 20,000 police maintained tight security at the meeting, which started peacefully with many of those gathered dancing to the music of drums and pipes.
One union confederation leader was the target of protests from within the crowd as he tried to make a speech and officials removed him from the meeting area to a nearby building amid scuffles, television channels reported.
Taksim square had been declared off-limits since the bloodshed during a May Day rally there in 1977 when gunmen, believed to be far-right militants aided by members of the intelligence services, fired on a peaceful crowd, triggering mass panic. The attackers were never caught.
The deaths came at a time of severe political tensions and street violence between leftist and rightist militants in Turkey, which culminated in a military coup in 1980.
Union leaders on Saturday tossed dozens of red carnations at the spot on the square where the victims were shot dead. A concert was to be held after the union leader speeches.
"It is our duty to everyone in this struggle to ensure that those behind the sad events of 1977 are caught and brought to justice," Mustafa Kumlu, the head of Turkey's biggest trade union TURK-IS, said.
There were minor scuffles when a group of workers protested Kumlu as he prepared to deliver a speech, and tried to climb up on the stage erected at the square, media reports said.
But the general mood was one of joy with little concern of possible scuffles or confrontation with police.
"I was here in 1977. That year, the celebration was also joyful, and then the shooting started," Gunal Oztekin, a 60-year-old retired worker, said.
"But, today I am not afraid. There will be only joy," he added.
Aydin Demir, a 44-year-old kiosk owner, said laborers had won a 33-year-long struggle for their right to rally at the square.
"We paid a heavy price to be here today. Thousands of comrades have been arrested, but now we get the result of our struggle," he said.
In the past, trade unions who tried to hold rallies at Taksim square in defiance of the ban met with a heavy police crackdown which left dozens injured and hundreds in detention.