Homeland chief: Homegrown attacks an increasing threat

FBI Director James Comey, center, flanked by Homeland Secretary Jeh Johnson, left, and Director of National Counterterrorism Center, Office of the National Intelligence, Nicholas J. Rasmussen, testifies on Capitol Hill in Washington, Tuesday, Sept. 27, 2016, before the Senate Homeland Security and Governmental Affairs Committee hearing on on terror threats. (AP Photo/Pablo Martinez Monsivais) (The Associated Press)

Senate Homeland Security and Governmental Affairs Committee Chairman Sen. Ron Johnson, R-Wis., left, accompanied by the committee's ranking member Sen. Tom Carper, D-Del., speaks on Capitol Hill in Washington, Tuesday, Sept. 27, 2016, during the committee's hearing on on terror threats. (AP Photo/Pablo Martinez Monsivais) (The Associated Press)

FILE - In this March 21, 2016, file photo, Homeland Security Secretary Jeh Johnson addresses an audience during a forum at John F. Kennedy School of Government on the campus of Harvard University, in Cambridge, Mass. Bombings in New York and New Jersey, and a stabbing attack in Minnesota the same day, underscore that homegrown attacks inspired by violent extremists are as much a threat to the United States as those directed by terrorists, the nation’s Homeland Security chief said. Johnson said the U.S. should be ‘building bridges to diverse communities' to defend the homeland. (AP Photo/Steven Senne, File) (The Associated Press)

The head of Homeland Security says recent attacks in New York and Minnesota underscore that homegrown attacks inspired by violent extremists are as much a threat to the United States as those directed by terrorists.

While all attacks are difficult to detect and prevent, Homeland Security Secretary Jeh Johnson says the U.S. and its allies continue to "take the fight militarily to terrorist organizations overseas."

Johnson tells Congress in prepared testimony that air strikes and special operations against the Islamic State terror group have killed many of its leaders. While it remains a threat, Johnson said the group has lost nearly half the populated areas it once controlled in Iraq and thousands of square miles in Syria.

Johnson and other officials are set to testify at a Senate hearing Tuesday.