WASHINGTON, United States (AFP)—US President Donald Trump demanded an investigation Wednesday into what he called “triple sabotage” after an escalator, teleprompter and sound system malfunctioned as he addressed the United Nations.

The UN has said the events which happened while Trump was at its headquarters in New York on Tuesday were accidental, and partly blamed them on White House staff.

But in a long, angry social media post, Trump described the string of mishaps on Tuesday as “very sinister,” called for people to be arrested and said the Secret Service was also probing.

“This wasn’t a coincidence, this was triple sabotage at the UN. They ought to be ashamed of themselves,” Trump said on his Truth Social platform.

“I’m sending a copy of this letter to the Secretary General, and I demand an immediate investigation. No wonder the United Nations hasn’t been able to do the job that they were put in existence to do.”

Footage showed the 79-year-old president and First Lady Melania Trump getting on the escalator at UN headquarters on Tuesday before it stopped with a lurch, forcing them to walk up.

Then, as he began his speech, he noted his teleprompter was not working.

He spent much of the rest of the speech bashing the world body, accusing it of funding illegal migration that was turning Western countries into “hell” and failing to support his peace efforts in Gaza and Ukraine.

But while Trump struck a mostly joking tone about the escalator on Tuesday, his mood hardened a day later.

“A REAL DISGRACE took place at the United Nations yesterday. Not one, not two, but three very sinister events!” he wrote.

Trump said the escalator stop could have been a “real disaster.”

“It’s amazing that Melania and I didn’t fall forward onto the sharp edges of these steel steps, face first,” he said.

Trump then complained that his teleprompter for his speech was “stone cold dark” for the first 15 minutes, and that the sound in the UN auditorium was “completely off.”

The US president called for the security tapes for the escalator to be saved, adding: “The Secret Service is involved.”

The United Nations did not immediately react to Trump’s statement.

But it insisted on Tuesday that there were simple explanations for it all.

A videographer from the US delegation “may have inadvertently triggered the safety function” on the escalator, causing it to stop, Stephane Dujarric, a spokesman for UN Secretary-General Antonio Guterres, said in a statement.

“Regarding the teleprompter, we have no comment since the teleprompter for the US president is operated by the White House.”