One of America's most respected news anchors has been suspended without pay for six months after admitting he lied about being shot at while travelling in a military helicopter in Iraq.

NBC has confirmed it has suspended Brian Williams with immediate effect for his "inexcusable" actions after he repeatedly claimed he and his camera crew came under rocket fire while reporting from the Iraq war in 2003.

Williams, who presents the Nightly News show, first made the claims during a 2003 broadcast detailing the incident.

His version of events came under scrutiny after he told the story during a special tribute at an ice hockey game for a military officer who, he claimed, saved his life after the Chinook helicopter he was riding in was shot down.

Several soldiers disputed the claims – including those on board the helicopter which was shot down – adding Williams and his crew had actually been travelling in a separate Chinook.

Flight engineer Lance Reynolds wrote on Williams' Facebook page: "Sorry dude, I don't remember you being on my aircraft. I do remember you walking up about an hour after we had landed to ask me what had happened."

Williams gave an on-air apology for giving "misleading" information about what happened, claiming the "fog of memory over 12 years" made him confuse two events.

"I would not have chosen to make this mistake," he said.

"I don't know what screwed up in my mind that caused me to conflate one aircraft with another."

Deborah Turness, president of NBC News, confirmed Williams is now suspended for six months without pay for his "wrong and completely inappropriate" behaviour.

Steve Burke, NBC Universal's chief executive, added: "By his actions Brian has jeopardised the trust millions of Americans place in NBC News. His actions are inexcusable and this suspension is severe and appropriate."

Further questions have now been raised about Williams' reporting, including his versions of events in New Orleans after hurricane Katrina and a claim that he was robbed at gunpoint in in the late 1970s while selling Christmas trees from the back of a truck.

Turness added: "We have concerns about comments that occurred outside NBC News while Brian was talking about his experiences in the field.

"As managing editor and anchor of Nightly News, Brian has a responsibility to be truthful and to uphold the high standards of the news division at all times."

At his peak, Williams was the most watched news anchor in the US and had recently signed a new contract with NBC for a reported $10m (£6.5m).