Donald Trump's advisor Kellyanne Conway used a fictitious terror attack to defend the US president's controversial immigration ban on seven Muslim-majority countries.

The campaign strategist mentioned the "Bowling Green massacre" during a live interview with MSNBC on Thursday, alleging that two Iraqi refugees were behind it.

"I bet it's brand new information to people that President Obama had a six-month ban on the Iraqi refugee programme after two Iraqis came here to this country, were radicalised and they were the masterminds behind the Bowling Green massacre," Conway said.

"Most people don't know that because it didn't get covered," she added.

While it is true that two Iraqi nationals were arrested in Bowling Green, Kentucky in 2011 for terror offences, there was no massacre. Nor is it true that the pair, who are serving life sentences, were even planning a terror attack.

In announcing their convictions in 2012, the US justice department said that "neither was charged with plotting attacks within the United States".

Conway's interview immediately attracted mockery from social media users, including Chelsea Clinton, who tweeted: "very grateful no one seriously hurt in the Louvre attack ...or the (completely fake) Bowling Green Massacre. Please don't make up attacks," referring to a real attack attempt in Paris earlier on Friday.

Hours after the gaffe, the Trump counselor gave an apology of sorts for her mistake, in which she attacked several media outlets for misrepresenting her views.