Brian Williams was suspended as managing editor and anchor of "NBC Nightly News" for six months after disputed accounts of his reporting in Iraq in 2003 led him to retract and apologize for the inaccuracies.

Williams' suspension is without pay and takes effect immediately, Deborah Turness, president of NBC News, said Tuesday in a memo to staff. Lester Holt, who stepped in as anchor this week after Williams took himself off the air, will continue in that role at the Comcast Corp.-owned network. Williams' salary is $13 million a year, according to the website Celebrity Net Worth.

Williams, 55, delivered his last broadcast of the top-rated evening news program on Feb. 6, two days after apologizing on-air and blaming his mistakes on the "fog of memory."

The newsman, who took over the anchor desk in 2004, said on Feb. 7 he would take a temporary break to "deal with the issues." NBC News said its investigation is continuing.

"Brian misrepresented events which occurred while he was covering the Iraq War in 2003," Turness said in the memo. "It then became clear that on other occasions Brian had done the same while telling that story in other venues. This was wrong and completely inappropriate for someone in Brian's position."

Williams' credibility came into question in late January over a story covered on the "Nightly News" in which Williams accompanied Sgt. Major Tim Terpak to a hockey game in New York, where the decorated veteran received a standing ovation.

During the piece, Williams said a helicopter he was aboard in 2003 was hit by a rocket-propelled grenade and forced down in Iraq. Williams made the same assertion in a 2013 interview on the "Late Show With David Letterman."

"In addition, we have concerns about comments that occurred outside NBC News while Brian was talking about his experiences in the field," Turness said.

Terpak led a unit that protected Williams and his team while they were stranded in the desert. But the aircraft they were in was following others that came under fire, NBC and Williams reported when correcting the original story after veterans disputed his claims.

Questions have been raised about Williams' accounts of his reporting on Hurricane Katrina in 2005. He has said he saw dead bodies float by in New Orleans' French Quarter, which had minimal flood damage.

Veteran journalist Richard Esposito, along with NBCUniversal general counsel Kim Harris, is leading the internal investigation.

Losing Williams could cost NBC in terms of ratings and advertising dollars. Network news anchors are "a symbol" for their companies, said David Westin, a former president of ABC News.

"That is the person who has lunch with the president the day of the State of the Union, and is there when big news happens," Westin said.

With its higher viewership, NBC is able to charge more for commercials. A 30-second spot on NBC goes for about $48,000, while ABC charges $37,000 and CBS gets $33,800, according to Nielsen.

A New Jersey native, Williams joined NBC in 1993 and served as chief White House correspondent and anchor of the "News With Brian Williams" on MSNBC and CNBC, according to the NBC News website. He replaced Tom Brokaw on the "Nightly News" in December 2004.