SYDNEY office workers were shaken today by emails and pictures circulated through the city allegedly showing police snipers on building rooftops.

Earlier, the sound of jet engines rumbled office buildings as security flyovers cleared the air above the city's CBD.

And on the harbour, a dozen zodiac boats packed with heavily-armed, black-clad security guards sped alongside the VIPs in their white luxury yacht.

It could have been a location shoot for a new James Bond film, but it was part of the blanket of security Australia has thrown over Sydney for the visit of US President George W. Bush.

NSW Police have yet to confirm or deny the authenticity of the pictures circulated by email, which show police officers in high-visibility vests perched on the top of a building with a large rifle.

After holding a news conference, Mr Bush and Prime Minister John Howard and their delegations boarded a sleek yacht at Man o' War Wharf and headed for Garden Island in Sydney Harbour.

Mr Bush and Mr Howard climbed to the upper deck to survey one of the world's most picturesque harbours on a rare drizzly spring day in Sydney, flanked by the zodiac boats and security jet-skiers.

Journalists followed behind on a rickety tour boat named Mystery Bay steered by a long-haired, bearded captain.

Mr Bush and Mr Howard waved to the journalists as they toured the harbour. Four jet-skiers fanned out in front of the yacht and led the way.

As a navy gunboat bobbed offshore, Mr Bush's yacht paused for a close-up view of Sydney's Opera House before heading to anchor.

Accompanied by Mr Howard, Mr Bush also had a look at the Royal Australian Navy's heritage centre at the Garden Island naval base, from which Australian sailors bound for Iraq ship out.

Mr Bush joined several hundred Australian troops and sailors for lunch beneath a giant outdoor tent.

He went through the buffet line and loaded his plate with steak, prawns, and corn on the cob.

"I'm looking forward to you buying me lunch today. I'm a meat guy," Mr Bush joked to Mr Howard ahead of the lunch.

Mr Bush rubbed shoulders with Australian defence chiefs and ordinary soldiers, sailors and air force crews.

Also in the throng was US Secretary of State Condoleezza Rice and Australia's defence minister.

Mr Bush and Mr Howard posed for photos with kitchen staff.

"I believe the work you are doing... is necessary for peace," Mr Bush told the crowd before listening to country music played by Australian Golden Guitar winner Felicity Urquhart.

"Thanks for making the sacrifice necessary for peace."

He acknowledged "these are tough times" but insisted: "We're going to win and we're going to succeed."

Mr Bush's words were met with polite applause.

With Reuters

News Limited

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Have you seen any police snipers in Sydney?