FILE PHOTO: National security adviser General Michael Flynn delivers a statement daily briefing at the White House in Washington U.S., February 1, 2017. REUTERS/Carlos Barria/File Photo

WASHINGTON (Reuters) - President Donald Trump’s national security adviser, Michael Flynn, resigned on Monday night in the midst of a raging controversy about his contacts with Russian officials before Trump took office, a White House official said.

Retired General Keith Kellogg, who has been the chief of staff at the National Security Council, has been named acting national security adviser.