7 arrested in apparent terror plot in Chicago

The arrests on Thursday by the FBI together with federal, state and local authorities were "part of an ongoing investigation into a terrorist-related matter," the US attorney's office in Miami said in a statement.

Media reports citing unnamed officials said seven people -- five US citizens and two foreigners, including a Haitian -- were arrested for plotting to attack the 110-story, 442-meter (1,450-foot) Sears Tower, the world's third tallest building, as well as other buildings in Miami.

Another person was arrested in Atlanta, Georgia, as well, according to television reports.

ABC television said the group had been infiltrated by a Federal Bureau of Investigation agent posing as an Islamic radical.

"The individuals arrested posed no immediate threat to our community," the US attorney statement said.

FBI director Robert Mueller told CNN television Thursday that operations were still under way.

"I can tell you that we do have an ongoing operation in Miami. We are conducting a number of arrests and searches, and we'll have more about that when the operation is concluded, probably (Friday) morning," Mueller said.

"Because it's an ongoing operation, I really can't get into details. But whenever we undertake an operation like this, we would not do it without the approval of a judge. We've got search warrants and arrest warrants and the like," Mueller said.

The Justice Department was planning to announce details of the plot at a news conference later Friday.

Law enforcement officials quoted Friday by The Washington Post said the plotting was in its early states and that no weapons or explosives had been seized as of late Thursday from the searched locations.

The arrests took place in Liberty City, a poor neighborhood north of Miami, according to local and national media.

Residents said that the men who were arrested appeared to be part of a cult of at least a dozen people, sleeping in a warehouse, dressing in military-like clothing and doing exercises.

CNN late Wednesday interviewed a member of the organization in Liberty City.

Brother Cory, as the black man with dreadlocks called himself, said he belonged to "Seas of David," repeatedly denying it was a terrorist group or that it had any ties to Al-Qaeda.