Sydney police tighten security as the city prepares to host 21 world leaders for the Asia-Pacific Economic Forum which begins on Sunday (September 2). A five kilometre metal fence was erected early on Saturday morning (September 1) across the central business district of Sydney as security precautions increase ahead of next week's APEC summit. The fence, supported by concrete blocks, are to prevent protesters getting close too meeting venues and delegation hotels. Series of protests are expected to mark APEC week between September 2-9. Leaders of the 21-member Asia-Pacific Economic Cooperation forum, including U.S. President George W. Bush, China's Hu Jintao and Russian President Vladimir Putin, will attend the summit in Sydney. The event will involve the biggest security operation in the nation's history, according to officials. "This security operation is enormous. We've got some three and a half thousand police officers supported by fifteen hundred defence force personnel to ensure that we have a multi-layered, multi dimensional security operation in place. It is extensive, it's certainly something we haven't seen by way of a security event in the past, and so we're preparing for it at an unprecedented level," said New South Wales Police Commissioner Andrew Scipione. In the weeks preceding APEC, police have conducted air, sea and ground practice operations to prepare security for the event. A 45-nautical-mile restricted airspace over Sydney will be enforced by FA18 Hornet fighter aircraft and police helicopters, while navy divers and special forces will patrol Sydney Harbour. The protesters are a prime concern for police, who have been given extra powers to arrest troublemakers and hold them in jail until the APEC summit is over. All courts in the city will be closed during APEC to free up police for security, a move which will also mean anyone arrested cannot be freed on bail. Many protesters say they want to protest peacefully but have become victims of police intimidation. "I think the police action has definitely been provocative. I think there's been a campaign of intimidation actually organised by the state government and the federal government and the police to try and scare people away from attending protests during APEC," said Alex from the Stop the War Coalition protest group. Sydney residents have also complained of the disruption to the city during the event, with a large part of the business district blocked off to cars and pedestrians by barricades. One small businessman who says he will suffer is cafe owner Les who fears his customers will be taking their annual leave to escape the APEC disruption. "We're still going to be paying the same amount of rent that we pay for every week but we're going to have a decrease because the people that we serve every week won't be here," he said. Thousands of Sydney residents plan to flee the city over the summit week, according to travel and real estate agents. APEC street security was dealt a blow on Tuesday (August 28) when the city's mounted police horses were diagnosed with equine flu and quarantined in stables for a month, ruling out a major crowd control measure. Police say they have backup crowd control measures, including a 12,000 litre (2,640 gallon) water cannon.