A former head of the Central Intelligence Agency (CIA) and National Security Agency (NSA) says Republican presidential frontrunner Donald Trump is making Americans "less safe" with his anti-Islam campaign rhetoric.

Michael Hayden, a top intelligence official under former president George W Bush, said what Trump does "is underscore and underpin" the narrative of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) of the "undying enmity" between Islam and the Western world.

"You don't have to be president for that kind of statement from someone so prominent in the American political system to have already made Americans less safe," Hayden told Al Jazeera's Mehdi Hasan, host of the UpFront programme.

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During his campaign, Trump had promised "a total and complete shutdown of Muslims" from entering the United States.

"Our country cannot be the victims of horrendous attacks by people that believe only in jihad, and have no sense of reason or respect for human life," Trump said.

Asked if Trump could be described "as a recruiting sergeant" for groups such as ISIL and al-Qaeda, Hayden replied: "Yes".

The retired US general was also critical of another Republican candidate, Ted Cruz, who called on American police "to patrol and secure Muslim neighbourhoods".

"We don't have radicalised communities in the United States," Hayden said. "We have some radicalised individuals, but we have it fully within our ability to create radicalised communities, and that kind of rhetoric [by Cruz]" risks "radicalising communities".

On the subject of the ongoing Hillary Clinton email controversy while she was secretary of state, Hayden called her action "inconceivable" and her explanation "incoherent".

Hayden also said it was likely that foreign intelligence agencies had hacked into Clinton's private emails.

"I would lose respect for scores of intelligence organisations around the planet if they weren't already thumbing through the emails," he said.

"And by the way, I would move heaven and earth as the director of NSA to get the unclassified emails of several foreign ministers."

But he stopped short of calling for her prosecution, adding that it was up to the Federal Bureau of Investigation to make that step. "Whether or not it represents a crime, I'll let the American justice system decide," Hayden said.