US president says Secret Service is investigating ‘three very sinister events’ at UN headquarters in New York.

United States President Donald Trump has demanded an investigation into “triple sabotage” he claims he suffered during a visit to the United Nations.

In a social media post on Wednesday, Trump said he had written a letter to UN Secretary-General Antonio Guterres demanding an inquiry into three separate incidents involving an escalator, a teleprompter and sound issues at the international body’s New York headquarters.

In an incident shortly before his speech to the UN General Assembly on Tuesday, Trump and First Lady Melania Trump were forced to walk up an escalator when the stairway came to an abrupt halt moments after they stepped on.

Trump appeared to brush off the incident at the time, joking about the escalator and a “bad” teleprompter during his speech.

But in a sharp shift in tone a day later, Trump branded the incidents as “three very sinister events” and said the US Secret Service had gotten “involved”.

“It’s amazing that Melania and I didn’t fall forward onto the sharp edges of these steel steps, face first. It was only that we were each holding the handrail tightly or, it would have been a disaster,” Trump wrote.

The incident was “absolutely sabotage”, Trump said, pointing to an article published in The Sunday Times that said UN staff had previously joked about shutting off escalators to humiliate the US president.

“The people that did it should be arrested!” Trump wrote.

Trump also claimed the sound system was “completely off” during his speech, and the audience “couldn’t hear a thing” unless they used the interpreters’ earpieces.

Mike Waltz, the US ambassador to the UN, echoed Trump’s demand for an investigation, calling the incidents “unacceptable” and “symptomatic of a broken institution that pose serious safety and security risks”.

A spokesperson for the UN did not immediately respond to a request for comment on Trump’s latest claims.

On Tuesday, UN spokesperson Stephane Dujarric said the escalator malfunction had possibly been caused by a videographer in Trump’s delegation accidentally triggering the emergency stop function.

Another UN spokesperson, Farhan Aziz Haq, said the teleprompter belonged to Trump’s team and referred inquiries to the White House.