Washington - A top aide to President Donald Trump has cited a 2011 "massacre" in Kentucky that never happened as a reason why the administration's temporary ban on immigration from seven Muslim-majority nations is necessary.Conway tweeted on Friday that she meant to say "Bowling Green terrorists".During an interview with MSNBC's Chris Matthews that aired on Thursday, Kellyanne Conway defended Trump's executive order on immigration last week by saying that former President Barack Obama instituted a similar policy for Iraqi refugees in 2011."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 between the Bowling Green massacre.Most people don't know that because it didn't get covered," Conway said.Conway is referring to a tightening of security checks for entry into the US after the May 2011 arrest of two men on charges of plotting to send weapons and money to al-Qaeda operatives waging an insurgency in their native Iraq.Waad Ramadan Alwan and Mohanad Shareef Hammadi were mistakenly admitted to the US as Iraqi refugees in 2009 and resettled in Bowling Green, Kentucky.Calling the Obama administration's actions a "ban" on Iraqi refugees is misleading. A formal ban wasn't announced by that administration, though there was a dramatic decline in the number of Iraqis allowed to move the US in 2011.Officials at the time cited an enhanced security clearance process for delaying Iraqi visa applications.Alwan and Hammadi are in prison after pleading guilty. They were never accused of plotting to launch attacks inside the US.Conway's comments have made fodder for jokes among social media users. "Bowling Green massacre" quickly became a top trending topic on Twitter with a flurry of tweets mourning the non-existent victims.