WASHINGTON — President Trump on Monday asserted that the news media was playing down the terrorist threat posed by the Islamic State, telling American military personnel that journalists were reluctant to report on the militant group’s attacks in Europe and “have their reasons” for failing to cover them.

Mr. Trump initially did not provide examples of a news media conspiracy to underplay terrorist attacks, and his comments appeared to ignore the vast amount of reporting on violence committed by the Islamic State and its supporters in the Middle East, Europe and the United States. Later Monday night, the White House released a list of what it said were 78 attacks from September 2014 to December 2016 that were carried out or inspired by the Islamic State. The White House said that “most have not received the media attention they deserved.”

The list included the major attacks in Paris; Brussels; San Bernardino, Calif.; and Orlando, Fla., that dominated the news for weeks. Other attacks overseas, lesser known to Americans, received extensive local coverage, like a shooting in Zvornik, Bosnia, in April 2015 in which one police officer was killed and two others were wounded.

The president’s speech was the second time in recent weeks that he has used an appearance before national security personnel — usually apolitical settings in which the focus is on strategy and sacrifice — to discredit journalists and exult in his election victory.