Attorney General Eric Holder is defending the Justice Department’s seizure of the work, home and cellphone records used by almost 100 reporters and editors at the Associated Press. The phones targeted included the general AP office numbers in New York City, Washington, D.C., and Hartford, Connecticut, and the main number for the AP in the House of Representatives press gallery. The action likely came as part of a probe into the leaks behind an AP story on the U.S. intelligence operation that stopped a Yemen-based al-Qaeda bombing plot on a U.S.-bound airplane. Critics say it could mark the biggest intrusion on freedom of the press under President Obama. Holder called the monitoring a necessary step for national security.

Eric Holder: “This was a very serious — a very serious leak, and a very, very serious leak. I’ve been a prosecutor since 1976, and I have to say that this is among, if not the most serious, it is within the top two or three most serious leaks that I’ve ever seen. It put the American people at risk. And that is not hyperbole. It put the American people at risk. And trying to determine who was responsible for that, I think, required very aggressive action.”

Holder says he recused himself from the probe into the leak last year to avoid a conflict of interest. He will appear before lawmakers today to answer questions on the case.