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By Emma Ross-Thomas

ISTANBUL, May 1 (Reuters) - Turkish police detained 580 people in Istanbul on Tuesday in street battles with leftist demonstrators protesting on the May Day anniversary of a mass shooting 30 years ago.

Police charged at hundreds of protesters, many from leftist organisations, kicking and clubbing them in the city's main Taksim Square and neighbouring streets.

Similar clashes occurred in other parts of Turkey's largest city as riot police and special forces fired tear gas and used water canons 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 in the clashes.

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.

Sunday's secularist marchers were demonstrating against the government's candidate for president, accusing the ruling AK Party of having a secret Islamist agenda. The political turmoil has unnerved financial markets.

"It's for the election and May 1. I came for both. Turkey is going through a tense period," said Erhan, a 28-year-old driver who declined to give his full name.

Authorities have enforced a strict security clampdown in the centre of Istanbul, Turkey's financial hub and largest city with 14 million inhabitants, to prevent May Day rallies which often attract tens of thousands of people and sometimes turn violent.

Some 17,000 police have been stationed across the city, CNN Turk television said. Metro stations, ferries and bus routes were closed and travel across the Bosphorus straits that divides the city curtailed.

The clampdown caused large traffic jams and forced the Istanbul stock exchange to start trading later than usual.

"The people of Istanbul should be patient. We have to take security measures," Istanbul Governor Muammer Guler told NTV television. "Those who protest without permission are responsible for what happens."

Guler was criticised for shutting down parts of the city.

"Guler has turned Istanbul into a prison," said Suleyman Celebi, head of the leftist union DISK.

Thirty years ago, 34 people were shot or trampled to death when an unidentified gunman opened fire on a May Day march in the city's Taksim square.

Authorities allowed a handful of union leaders to lay red carnations at the site of the deaths. Later hundreds of people gathered at the square to protest.

It was the first time since the 1980 military coup that authorities have allowed some May Day protesters to enter the Taksim square.

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