Turkish police are preparing for a massive security operation in Istanbul, where trade unions are planning a large May Day rally on Thursday. Since 1980, trade union rallies have been banned in Istanbul's Taksim square, which was the site of a bloody clash with police in 1977. Dorian Jones has this report for VOA from Istanbul.

Thousands of police have had their leave canceled, and the city governor has announced that large parts of the city will be closed down ahead of May Day celebrations.

Three of Turkey's largest trade union confederations have said they will challenge a government ban on celebrating May Day in Taksim square in the heart of Istanbul. Prime Minister Recep Tayyip Erdogan condemned the unions.

Turkish PM Tayyip Erdogan walks past a military guard of honour in Ankara, 30 Apr 2008

Mr. Erdogan says he believes there was what he called "ill intention" behind this request. He says it is a request geared toward disrupting public order.

The prime minister says there are alternative locations in Istanbul to Taksim square to celebrate May Day. But Taksim square has major symbolic importance to trade unionists. In 1977, 37 people were killed when unknown gunmen opened fire on a crowd of hundreds of thousands of people who were celebrating May Day.

Defne Sandilci, who attended the 1977 protest, remembers the panic that erupted as the gunfire rang out.

"We saw people shouting there, I could see them quite clearly, there was a massive panic there and shouting and lots of people died," said Sandilci.

Since the military seized power in 1980, trade union protests have been banned in the Taksim square, but some smaller civic demonstrations have been held there and trade unionists have been pressing the government to lift the ban to allow their members to commemorate those killed in 1977.

Turkish riot police use a slingshot to disperse leftist demonstrators during a May Day rally in Istanbul, 01 May 2007

In a last minute bid to defuse the row Mr. Erdogan said a small delegation could lay a wreath at the square. But the labor unions rejected the offer. Head of one of the largest trade union confederations, Tayfun Gorgun, workers have a right to stage the May Day rally.

Gorgun says this is "our warning to the government: do not ignore the demands of 10 million workers, do not ban the May 1 celebrations that are a democratic right."

The minister of the interior says any attempts to break the government ban will be dealt with harshly. Several hundred thousand trade unionists are expected to turn up for the May Day celebrations.