IOC president Jacques Rogge warned on Thursday that deadly bombings in neighboring Turkey could prompt even tougher security measures for the Athens Olympics.
"There is a danger of terrorism and that danger is not limited to a certain number of countries," Rogge said. "It can happen in Greece as it could happen in any other country that I could name."
Security concerns in Athens have heightened since this month's attacks in Istanbul, Turkey, which were claimed by al-Qaeda and killed 55 people, including the bombers.
"Security is the No. 1 priority," Rogge said at a news conference. "Everything that is humanly possible has been put into place. No stone has been left unturned."
Athens organizers have said they do not want Athens to resemble an armed camp during the Aug. 13 to 29 Olympics.
But Rogge said stricter security would be tolerated if necessary.
"If the result of this means that athletes, spectators or officials have to undergo more security checks, let it be so," the International Olympic Committee president said.
"If we see police and-or armed forces at the games, let it be. If it is needed, then we are glad that they are there."
Greece has already budgeted more than US$750 million to protect the games and is receiving advice on fighting terrorism from seven countries, including Britain, the US and Israel.
Britain's top anti-terrorism official, David Veness, who visited Athens this week, called the Istanbul attacks a "wake up call" to Europe, and said Olympic security plans should reflect the higher threat level.
"Tragically, the events of recent days have demonstrated that Europe itself is a potential stage for these attacks," Veness, assistant commissioner of the Metropolitan Police, told private Mega television's Files program.
He was the second senior police official to visit Athens in November. FBI Director Robert Mueller visited on Nov. 7 to review security preparations.
Following the Istanbul attacks, security at British and American sites in Athens has been increased. Concrete barriers were placed on roads around the British Embassy Thursday to prevent the possibility of a car-bomb attack.
Rogge was in Athens for a three-day visit to attend a ceremony presenting the route of the flame that will burn at the Athens Olympics.
The torch will go on an unprecedented six-continent journey that will include groundbreaking visits to South America and Africa.