ISTANBUL - Police in Istanbul fired tear gas and rubber bullets to break up a group of May Day demonstrators on Monday, a Reuters witness said, as authorities detained more than 200 people at protests around the city.Protests for May Day, the international workers' holiday, are an annual occurrence in Turkey and have in the past been characterized by widespread police actions against demonstrators.Protests were expected to be more subdued this year after unions said they would not attempt to march on Taksim Square, a traditional rallying point for anti-government protests that has been declared off-limits for demonstrators.Police presence was heavy across the city, with helicopters buzzing overhead. Tensions are particularly high after President Tayyip Erdogan narrowly won a referendum last month giving him sweeping new powers.Police in the Mecidiyekoy neighborhood used tear gas and rubber bullets on a group of protesters who were attempting to march towards Taksim Square. They were shouting "Taksim is ours and it will remain ours."The square became the focal point for weeks of anti-Erdogan demonstrations in 2013. Two demonstrators who managed to reach it were detained shortly after they unfurled a banner, Dogan news agency said.