The chairman of the Senate Homeland Security Committee says domestic terrorism is a real and growing danger.
Sen. Joe Lieberman, a Connecticut independent, says the political discourse in the U.S. turns extreme and incendiary at times, and that can lead some people to take radical actions.
Federal authorities report an uptick in the activities of domestic extremist groups in the last year.
Noting the recent bombings in Moscow, Lieberman says more must be done to protect trains, subways and buses in the U.S.
Lieberman appeared Sunday on NBC's "Meet the Press."
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