Canadian athletes are among the many whose fears have been piqued following a bomb attack that marred Greece's entry into the final 100-day countdown to the summer Olympiad.

No one was injured in the explosions, but they did cause serious damage to the police building and nearby apartment blocks in the densely populated Kalithea suburb, which houses several hotels that Olympic officials will be using during the Games.

"This is an isolated incident which does not affect whatsoever the safety of the Olympic preparation," Premier Costas Caramanlis assured reporters on Wednesday.

The International Olympic Committee also said it was confident that the incident wasn't linked to the Games.

"The IOC understands from the Greek authorities that, so far, nothing indicates this morning’s incident was related to preparations for this summer’s Olympic Games," the IOC said in a statement.

In spite of the assurances, Canada's Department of Foreign Affairs updated its travel report Wednesday, urging Canadians who visit Greece to "exercise caution and maintain a high level of personal security awareness at all times and in all places."

That warning could be little comfort to Canada's Olympians trying to focus on their sport now that the Games are less than three months away.

Canadian judo team member Amy Cotton is one who hopes claims the series of explosions was not linked to international terrorism are true.

"It's scary, but hopefully it will be under control by the time we get there," told CTV News.

In an effort to safeguard the Games, which run from Aug. 13 to 29, a staggering $750 million US has been budgeted for event security. Authorities plan to deploy more than 50,000 security personnel, including soldiers, during the world sporting event.

Greece has also asked NATO for help with air and sea patrols as well as protection against weapons of mass destruction.

Preparations for the Games are said to be behind schedule, hampered by construction delays and other glitches.

U.S. officials fear that construction delays may undercut efforts to test security systems ahead of the Olympics. For that reason, a Greek delegation, led by Public Order Minister George Voulgarakis and the head of the Greek police, is in Washington for talks on efforts to safeguard the Games.

Last week, the IOC announced it had taken out an unprecedented insurance policy, worth $170 million, to protect against the Athens Games being called off because of war, terrorism or natural disasters.

Despite the massive security effort, some American athletes have already signalled fear for their safety could keep them from the Games.

Tennis star Serena Williams, for one, has already said she's thinking about staying home.

"If it became a concern where I personally wouldn't feel comfortable, then I wouldn't go to Athens -- because I like my life."

In Canada, the Olympic Committee says it's not aware of any competitors considering dropping out of the Olympics, and besides, there's no cause for alarm.

"The security that's in place in Athens today is nowhere near, doesn't approach the security that'll be in place during the Olympic Games," COC member Michael Chambers said.

But former Olympian Thelma Wright, who ran for Canada in Munich three decades ago, says it's right to worry.

"It is a huge political stage. The world is watching," she told CTV, recalling her experience running just hours before Palestinian gunmen launched a terror attack that left 11 Israeli athletes dead.

"If there are people out there who want to cause some damage or undue strife, this is a place they'll be recognized."

Regardless, sprinter Nicolas Macrozonaris says he's not losing any sleep.

"If I was American I'd be terrified, but I'm Canadian."