There are reports that a car bomb has exploded outside the US State Department in Washington.
This is the fifth explosion in an hour and a half in a spate of major terrorist attacks on the United States.
Tony Blair postponed his TUC speech in Brighton and spoke of the mass terrorism, saying it is “the greatest evil in our midst today”.
He also expressed sympathy for President Bush and the American people.
Palestinians in the West Bank and Gaza Strip have phoned news headquarters in Jerusalem, strenuously denying responsibility for the attack.