Donald Trump
Republican presidential candidate and front-runner Donald Trump arrives at a campaign rally at the Richmond International Raceway October 14, 2015 in Richmond, Virginia. A New York real estate mogul and reality television star, Trump is now in a statistical tie with retired neurosurgeon Ben Carson in a Fox News survey of likely Republican voters released Tuesday.Chip Somodevilla/Getty Images

Republican front-runner Donald Trump claims that he could have prevented 9/11 if he had been president at the time. During an interview on Fox News Sunday, Trump said that because he is "extremely, extremely tough on immigration" the perpetrators of the attacks would not have been in the US.

"I believe that if I were running things ... I doubt that those people would have been in the country," he told Fox News. Trump's comments are the latest in an ongoing feud with fellow Republican candidate, Jeb Bush, the brother of then-President George W Bush. Jeb Bush first defended his brother against Trump's attacks during the second GOP presidential debate.

"You remember the rubble at the World Trade Centre? He sent a clear signal that the United States would be strong and fight Islamic terrorism, and he did keep us safe," Bush said at the debate. Trump retorted, "You feel safe right now? I don't feel so safe."

In his latest interview, Trump said he does not blame George W Bush for the attacks, but also criticised his time in office. "I'm not blaming George Bush," he said. "But I don't want Jeb Bush to say, 'My brother kept us safe,' because September 11 was one of the worst days in the history of this country."

Trump also took to Twitter to continue taking jabs at the former Florida governor. He tweeted, "Jeb, why did your brother attack and destabalize the Middle East by attacking Iraq when there were no weapons of mass destruction? Bad info?" The real estate mogul turned politician followed up with: "Jeb Bush should stop trying to defend his brother and focus on his own shortcomings and how to fix them."

Not one to take the criticism quietly, Bush shot back at Trump during an interview on CNN's State of the Union on 18 October. "My brother responded to a crisis, and he did it as you would hope a president would do. He united the country, he organised our country and he kept us safe. And there's no denying that. The great majority of Americans believe that," he said.

Bush added, "And I don't know why he keeps bringing this up. It doesn't show that he's a serious person as it relates to being commander in chief and being the architect of foreign policy." Trump responded by retweeting messages from followers, including one by conservative Ann Coulter.