Turkish police have taken extraordinary measures to prevent demonstrations on May Day.
136 people have been detained, in particular around Taksim Square in Istanbul which is under security lockdown today.
Opposition parties and a number of unions said they are determined to march to the square from the Besiktas neighbourhood.
Prime Minister Ahmet Davutoglu emphasised that only token gatherings would be permitted. He also hinted that larger rallies would be dispersed by police.
Only a small group of unionists were allowed into the square for a modest remembrance ceremony for the victims of May Day 1977, when 34 people were killed.