The U.S. government announced that it raised the nation's "terror alert" to orange at a news conference held in Washington on Sunday.
Secretary of the Department of Homeland Security Tom Ridge ordered the threat level increased to "high" from the "elevated" yellow status. On the five-point scale, orange is the second-highest level.
Saying that risks are "perhaps greater now than at any point since Sept. 11, 2001," Ridge cited increased chatter picked up by U.S. intelligence about attacks during the holiday season as the reason for the move.
The increase means security will be tightened at airports, border crossing and ports.