Speaking after arriving in the Nigerian capital Abuja, Rato said: "Terrorism has a clear strategy of attacking all types of institutions, domestic and international. I think we should not fool ourselves, terrorism is an enemy of all persons and institutions that are related to freedom."
Intelligence warnings of threats by Osama bin Laden's militant al Qaeda network to attack the IMF, World Bank and New York Stock Exchange prompted the United States to issue a "high" level alert on Sunday for financial institutions in New York and Washington.
Rato, in his first comments to the media since the alert, said he had not considered cancelling his trip to Africa which also includes visits to Gabon and Uganda.
An IMF official said the Fund, located a few minutes' walk from the White House, would open for business as usual on Monday despite the warning.