Organisers have left no stone unturned in their efforts to ensure the security of the Athens 2004 Games, International Olympic Committee president Jacques Rogge said on Thursday.

"Everything that's humanly possible has been put in place," Rogge told reporters during a visit to the Greek capital. "If it means spectators and officials have to undergo more security checks so be it."

Athens Games organisers have drafted the biggest ever security plan costing 650 million euros following the September 11, 2001 attacks on U.S. cities and the wars in Afghanistan and Iraq.

But twin bombing attacks in neighbouring Turkey in the past two weeks have raised alarm bells with organisers as fears of a potential overspill have increased.

"No stone has been left unturned...if we see more armed forces, if certain measures have to be taken then let it be," he said.

Greece will deploy more than 45,000 armed security officers across the country before and during next year's Olympics, three times as many as in the Sydney 2000 Games.

It has also said assistance will be provided by dozens of foreign nations as well as NATO.

Rogge said he had addressed the issue with the Greek government and demanded assurances for the Games' safety.

"The governments have always delivered," Rogge said.

"We have hired former Olympics security chiefs and a great number of countries are collaborating with the Greek government."

Greece has set up the first ever Olympic security advisory group, comprising seven countries, to increase intelligence and know-how ahead of the Games.

The seven nations are Britain, France, the United States, Spain, Australia, Germany and Israel.

"No one can guarantee 100 percent security," he said. "It's all about minimising risks."