USS Cole
The so-called "special warning" refers to intelligence indicating that terrorists may use speedboats to attack a western ship in east African waters and has been broadcast over an open channel to seafarers since last week.

"As of early 2005, the United States government has received unconfirmed information that terrorists may attempt to mount a maritime attack using speedboats against a western ship possibly in East Africa," it says.

"This information is unconfirmed and the United States is not aware of additional information on the planning, timing or intended targets of the maritime attack," the warning says.

The threat applies to inland channels, ports, territorial and international waters in and off the coasts of the Comoros, Djibouti, Eritrea, Kenya, Madagascar, Mauritius, Mozambique, the Seychelles, Somalia, Sudan and Tanzania, according to the warning.

The threat information contained in the warning was compiled by the US State Department in coordination with the departments of defense and commerce and the Central Intelligence Agency.

It has been broadcast to US military ships, the Coast Guard and US shipping companies over an open-channel satellite since March 11, according to the US National Geospatial-Intelligence Agency which disseminates "special warnings."

Special warnings "are issued in response to extraordinary political threats to US shipping, including war, terrorist threats and seizure and harassment of vessel by government authorities," according to the State Department.