U.S. law enforcement officials are warning that al-Qaida may be planning a new round of "spectacular" terrorist attacks.
Using unusually strong language, the Federal Bureau of Investigation says al-Qaida may be planning attacks intended to inflict mass casualties and severe damage to the U.S. economy.
The FBI bulletin was issued on its Web site Friday, and circulated to local law enforcement officials nationwide.
The warning says that what it calls "spectacular" attacks by al-Qaida could target the aviation and petroleum industries, as well as the nuclear power sector. The bulletin says that highly symbolic national landmarks could also be at risk, and that any attack would be designed to inflict what it calls "maximum psychological trauma."
Senate Democratic Leader Tom Daschle says the new FBI warning is cause for concern.
"But we shouldn't minimize the danger, the threat that is now posed by al-Qaida. It is still there, and we have to deal with it; we have to be ready for it," senator Daschle said.
The new terror alert comes in the wake of the release of an audiotape this week purportedly containing the voice of Osama bin Laden, warning of further attacks. U.S. intelligence agencies have also reported an increase in intercepted communications from suspected terrorists that could signify an impending attack.
The new warning contains no information about the timing, location or method of possible attack. Because of a lack of specific information, federal officials have decided for now not to increase the nationwide level of alert that currently stands at "elevated risk."
U.S. officials are also on heightened alert following the execution late Thursday of Pakistani national Mir Aimal Kasi. Kasi was put to death in Virginia for killing two men and wounding three others outside the headquarters of the Central Intelligence Agency in 1993.