(CBS) The Justice Department Thursday arrested four U.S. residents and charged them and four others with supporting a group blamed for "numerous violent terrorist activities."

A 50-count indictment, returned by a federal grand jury in Tampa, Fla., charges that the men are members of the Palestinian Islamic Jihad, designated by the United States as a terrorist organization.

Attorney General John Ashcroft, announcing the indictments, called the group "one of the most violent terrorist organizations in the world."

Among three people arrested in Florida was Sami al-Arian, a University of South Florida professor, who Aschroft alleged was the Palestinian Islamic Jihad's North American leader and a secretary of the council that governs the PIJ worldwide.

In Florida, Al-Arian was seen being led in handcuffs to FBI headquarters in Tampa after the arrest.

"It's all about politics," Al-Arian told reporters as agents led him inside.

Besides Al-Arian, two people were arrested in Tampa, one person was in custody in Chicago. The other four live abroad and have not been arrested.

The other two picked up in Tampa were identified as Sameeh Hammoudeh, 42, and Hatim Naji Fariz, 30. Ghassan Ballut, 41, appears to be the man arrested in Illinois.

The indictment charges the eight men with operating a criminal racketeering enterprise since 1984 that supported Palestinian Islamic Jihad and with conspiracy to kill and maim people abroad, conspiracy to provide material support to the group, extortion, perjury and other charges.

The defendants allegedly provided financial support through a number of U.S.-based entities, resolved internal conflicts, helped communicate claims of responsibility for terrorist actions and made false statements to immigration officials to help terrorists.

Erin Moriarty of 48 Hours Investigates once confronted him over a statement he made saying, "Let us damn America. Let us damn Israel (and) their allies until their death."

On the show, Al-Arian said, "Right. That's a stupid comment. But what really was meant here is the American policy. It's a figure of speech. Death to Israel means death to the system. It's like saying death to the occupation."

As CBS News Correspondent Jim Stewart reports, Al-Arian isn't the first South Florida professor with ties to terrorism. Professor Ramadan Abdullah Shallah left teaching to become the actual head of Palestinian Islamic Jihad.

The only real surprise is that this indictment took so long. It's been an open secret the FBI had been watching the men. Some of the phone taps referred to in the indictment, in fact, go back over 8 years.

In addition to the arrests, Ashcroft said searches were under way Thursday at six locations in Tampa and one in Illinois.

CBS News legal consultant Andrew Cohen says the vast scope of the indictment represents the full arsenal of charges the government is able to use in its domestic law enforcement fight against terrorism and terrorist organizations. Each defendant faces up to life in prison if convicted.

Ashcroft said the indictment was a signal to terror supporters.

"Our message to them and to others like them is clear: We make no distinction between those who carry out terrorist attacks and those who knowingly finance, manage or supervise terrorist organizations," he said.

The attorney general claimed the Palestinian Islamic Jihad's sole purposes was to destroy Israel and end Western influence in the Middle East. Quoting from the PIJ manifesto, Ashcroft said the group considers "the martyrdom style as the only choice" and calls the United States "the Great Satan America."

He linked the PIJ to several terrorist attacks in Israel and the occupied territories, including:

• An April 6, 1994 car bombing that killed nine people aboard a bus.
  
  
• A suicide bombing on Nov. 11, 1994 that killed three.
  
  
• Double suicide bombings on Jan. 25, 1995 that killed 22 people.
  
  
• A bomb attack last June that took 20 lives and injured 50.

Among the 100 people whose killings are blamed on the organization in Israel and the territories are those of two U.S. citizens: Alisa Flatow, 20, and Shoshama Ben-Yishai, 16.

Those arrested in the United States Thursday were described as setting up a terrorist cell at the University of South Florida.

Al-Arian, who has lived in the United States since 1975 and taught at USF since 1986, has consistently denied any connection to terrorists. The U.S. Attorney's Office in Tampa said last year that Al-Arian was under federal investigation, but refused to elaborate.

Al-Arian and his brother-in-law, Mazen Al-Najjar, founded the World and Islam Studies Enterprises, a now-defunct Islamic think tank at the university. The group was raided by the FBI in 1995. Al-Arian also founded the Islamic Concern Project Inc. in 1988.

Al-Najjar, who also had taught at the university, spent more than 3½ years in jail on secret evidence linking him to terrorists. He was released in 2000 but arrested again in November 2001 and deported last August.

The university placed Al-Arian on forced leave and banned him from campus shortly after the Sept. 11 terrorist attacks and his subsequent appearance on a talk show on Fox News Channel.

He was quizzed about links to known terrorists, and asked about tapes from the late 1980s and early 1990s in which he said "Death to Israel" in Arabic. The university says that hurt the school's fund-raising efforts and resulted in threats being made against the school.

Al-Arian has said that he has never advocated violence against others and that his words were a statement against Israeli occupation.

Michael Reich, a university spokesman, said the arrest of Al-Arian was "disconcerting but not surprising." He said university President Judy Genshaft would meet with the school's lawyers Thursday to discuss the arrest.

Last month, the faculty union at the University of South Florida filed a grievance on Al-Arian's behalf, saying that banning him from campus violated the union's contract, Al-Arian's right to academic freedom and its own policy of nondiscrimination on the basis of ethnicity and religious affiliation.

Cohen reports that the indictment clearly is the result of massive government surveillance and other law enforcement work against several different people here and around the world.

The attorney general, who has been at the forefront of efforts to expand the surveillance authority of federal agents, said Thursday's indictment was based partly on "now declassified national security wiretaps."

Asked if recent changes to federal surveillance rules in the Patriot Act and subsequent litigation had an impact in this probe, Ashcroft said he could not say how those changes played into this particular case.