In a potentially ominous development, the Secret Service has reportedly spoken with the campaign of Donald Trump over a controversial remark in which he appeared to propose shooting his rival Hillary Clinton.

A major US broadcaster said that officials from the agency, one of the country's oldest federal law enforcement bodies and responsible for the security of the president, along with the two presidential candidates, had spoken with the campaign several times. CNN said the move followed a speech on Tuesday about the Second Amendment in which Mr Trump appeared to say the only way to stop Ms Clinton from appointing liberal judges if she were elected president would be to kill her.

“Hillary wants to abolish, essentially abolish the Second Amendment,” he had said, referring to the piece of legislation that gun rights activists claim gives them the right to bear weapons. “If she gets to pick her judges, nothing you can do, folks. Although the second amendment people, maybe there is.”

Mr Trump has strongly denied claims that he was threatening Ms Clinton and told Fox News that he was the victim of a biased media. “Give me break,” he said.

“Nobody in that room thought anything other than that. This is a political movement. This is a strong powerful movement, the Second Amendment. Hillary wants to take your guns away. She wants to leave you unprotected in your home.”

The Clinton campaign responded immediately. “This is simple - what Trump is saying is dangerous. A person seeking to be the president of the United States should not suggest violence in any way,” said campaign manager Robby Mook.

On Wednesday, Hillary Clinton, speaking in Des Moines, Iowa, said the remark was further evidence of what she termed his unsuitability to occupy the White House.

“Words matter, my friends, and if you are running to be president or if you are president of the United States, words can have tremendous consequences. Yesterday, we witnessed the latest in a long line of casual comments from Donald Trump that crossed the line,” she said.

“His casual cruelty to a Gold Star family, his casual suggestion that more countries should have nuclear weapons, and now his casual inciting of violence. Every single one of these incidents shows us that Donald Trump simply does not have the temperament to be president and commander in chief of the United States.”

Meanwhile, speaking at a rally in Abingdon, Virginia, Mr Trump sought to turn the spotlight onto Ms Clinton and the release of more emails from during her time as secretary of state that suggested a close relationship between the Clinton foundation and the US State Department.

“You pay, and you’re getting things”,” he said. “It’s really, really bad.”

He said that if the emails had been about him, the media would have made it their biggest stories. “The media is totally dishonest,” he said.

The New York tycoon also sought to focus on his support for the Second Amendment, which he has repeatedly claimed Ms Clinton is seeking to revoke, despite their being no evidence of such an intention.