"The FBI has received unconfirmed information that a domestic group is planning to disrupt the (convention) by attacking media vehicles with explosives or incendiary devices," the FBI said in a statement.
The FBI didn't release any other details, including the name of the group, or when it might attack. Television stations were warned Thursday. The four-day convention begins Monday at the FleetCenter, where several satellite trucks are already stationed.
The FBI's Boston Joint Terrorism Task Force is investigating.
Several local TV stations planned a conference call Friday to determine if extra security is needed. Already, local stations have trucks at two main sites and are sharing the cost of police details.
Security is a top concern at the Democrats' gathering in Boston — the first major political convention since Sept. 11. Authorities have announced plans to close a 6-mile stretch of Interstate-93 that runs near the FleetCenter. Trash cans have been removed because of the danger that they will be used to hide bombs.
The Boston Globe reports that a federal judge has upheld a plan by Boston police to confine protesters to a small area surrounded by concrete barriers, fencing and razor wire.
The newspaper said prosecutors had told District Judge Douglas P. Woodlock that there is intelligence that some protesters plan to use sling-shots to fire ball bearings at police — a tactic used at the 2000 Democratic convention in Los Angeles.
Protest groups challenged the police-designated protest zone, saying it restricted free expression.
Besides the threat of domestic radicals and violent demonstrators, the convention takes place under the shadow of warnings by U.S. officials that al Qaeda may be planning an attack intend to disrupt the presidential election.