The Secret Service is investigating threats made against President Barack Obama by the former butler of presumptive Republican nominee Donald Trump.

Anthony Senecal, 74, who worked for 30 years at the tycoon’s Palm Beach mansion, has posted a series of incendiary comments on his Facebook page.

In one message, dated September 2015, he said the military should hang Mr Obama for treason and other “high crimes”.

In May last year he wrote that Mr Obama should be “dragged from the white mosque and (hanged) from the portico”.

Donald Trump Jr. And Vanessa Haydon Wedding - Arrivals

Mr Senecal worked as butler at the Mar-a-Lago club in Florida until 2009

He wrote: “To all my friends on FB, just a short note to you on our pus headed ‘president’!!!

“This character who I refer to as zero (0) should have been taken out by our military and shot as an enemy agent in his first term!!!!!

“Instead he still remains in office doing everything he can to gut the America we all know and love.”

Mr Senecal, who worked for Mr Trump until 2009, confirmed to magazine Mother Jones that he had written the posts.

He has stressed in some of the entries on Facebook that he does not speak for Mr Trump.

Mr Trump’s campaign has been quick to condemn Mr Senecal’s posts.

Spokeswoman Hope Hicks said in a statement: “Tony Senecal has not worked at Mar-a-Lago for years, but nevertheless we totally and completely disavow the horrible statements made by him regarding the president and first family.”

After he retired in 2009, Mr Trump kept Mr Senecal on as an unofficial historian at Mar-a-Lago, according to The New York Times.

On Thursday, the Secret Service said it was “aware of this matter and will conduct the appropriate investigation”.

Typically, Secret Service investigations involve a face-to-face interview with someone believed to have made threats against the president or other protected officials.