Turkish Prime Minister Recep Tayyip Erdogan said on Tuesday he would not allow May Day gatherings on Istanbul's Taksim Square, the scene of protests that have dogged the government for months.
A similar decision in May last year to ban the use of the square - a traditional and symbolic rallying point - led to violent clashes between police and protesters which were followed by a wave of nationwide anti-government demonstrations in June.
"Those who insist on celebrating it here (in Taksim Square) are just saying: 'I am ready for clashes," Erdogan said at a meeting of his parliamentary party.
"Give up on your hopes of Taksim. Do not engage in a fight with the state. Do not disturb the peace of our people. Our people do not want to see streets where stones and Molotov cocktails prevail," he said.
"We will not tolerate this. You are not above the law."
Erdogan has instead suggested other venues, and offered free transport on May 1.
The leftist unions have already vowed to ignore the ban.
On Monday, police fired tear gas at members of the May 1 Committee - made up of unions and civil society groups - to prevent them from issuing a statement about May Day demonstrations in Taksim.
Eight people died when a relatively small environmentalist movement to save Istanbul's Gezi Park - adjacent to Taksim - evolved into a nationwide wave of protests against Erdogan.
Fresh protests have erupted over a graft scandal implicating key Erdogan allies and controversial measures taken by the prime minister including an Internet crackdown that saw Twitter banned for two weeks.
Despite the protests and the corruption scandal, Erdogan's Islamist-rooted Justice and Development Party scored a crushing victory in March 30 local elections. - Sapa-AFP