Turkish police detained 580 people in Istanbul on Tuesday (May 1) during street battles with demonstrators protesting on the anniversary of a mass May Day shooting 30 years ago. Police charged hundreds of protesters, kicking and clubbing them in the city's main Taksim Square and neighbouring streets, a Reuters reporter said. Similar clashes occurred in other parts of Turkey's largest city as riot police and special forces fired tear gas and used water cannon to break up the crowds. A cloud of tear gas hung over the city's main pedestrian street. It was not clear how many people were hurt. The government will be watching to see whether an official May Day march in Istanbul later on Tuesday turns into a protest against the ruling AK Party following a demonstration by up to a million people in the city on Sunday (April 29). Sunday's marchers were demonstrating against the government's choice for president, accusing the party of having a secret Islamist agenda. The political turmoil has unnerved financial markets. Authorities have enforced a strict security clampdown in the centre of Istanbul to prevent May Day rallies which often attract tens of thousands of people and sometimes turn violent. About 17,000 police have been stationed throughout the city. Metro stations, ferries and bus routes were closed and travel across the Bosphorus strait that divides the city was restricted. The clampdown caused massive traffic jams and forced the Istanbul stock exchange to start trading later than usual. Thirty years ago, 34 people were shot or trampled to death when an unidentified gunman opened fire on a May Day march in Taksim square. Authorities allowed a handful of union leaders to lay red carnations at the site of the killings. Later, hundreds of people gathered at the square to protest. It was the first time since the 1980 military coup that authorities had allowed May Day protesters to enter Taksim Square.