US presidential candidate Kamala Harris has mocked rival Donald Trump after bizarre behaviour at a campaign event that prompted concerns for his health.

“Hope he’s OK,” Harris wrote on X, after Trump cut short a question-and-answer session at a rally near Philadelphia to sway to music on stage in front of the crowd for about 40 minutes.

Harris’s comment was a reply to a post from her own Democratic campaign account.

“Trump appears lost, confused, and frozen on stage as multiple songs play for 30+ minutes and the crowd pours out of the venue early,” it said on Tuesday (local time).

The post was one of many on social media showing 78-year-old Trump, the Republican nominee for the November 5 election, swaying to music while standing on the stage.

Hope he’s okay. https://t.co/WGhGteFpjm

— Kamala Harris (@KamalaHarris) October 15, 2024

It came after a frustrated Trump had to twice halt his rally for medical emergencies, before deciding to take what The New York Times called an “odd town hall detour”.

“Would anybody else like to faint?” Trump asked.

“Let’s not do any more questions, let’s just listen to music. Who the hell wants to hear questions, right?”

The NYT wrote that Trump “seemed to decide in the moment that it would be more enjoyable for all concerned – and, it appeared, for himself – to just listen to music instead”.

“Trump had his staff fire up his campaign playlist, standing on the stage for about half an hour and swaying to songs as his crowd slowly dwindled.”

Songs such as the Village People’s YMCA and Rufus Wainwright’s version of Hallelujah played, while Trump also watched a Sinead O’Connor video and rocked a bit to Elvis. Some in the crowd left.

“Nobody’s leaving. What’s going on? There’s nobody leaving. Keep going,” Trump said at one point.

He eventually left the stage – shaking hands along the way – to a final hit.

This is not normal. Particularly for someone running for President. He stood there and swayed for over 30 minutes. Something is very off with this man’s brain.

— Barbra Streisand (@BarbraStreisand) October 15, 2024

Campaign spokesman Steven Cheung called the event a “total lovefest”, telling Time magazine that “Trump has more energy and more stamina than anyone in politics, and is the smartest leader this country has ever seen”.

“He does multiple public events every single day and the public can see he is sharper and more focused than ever before because the future of America is at stake … People know President Trump is the strongest and most capable candidate. He has outworked and outpaced Kamala.”

That thing Trump did last night is not explainable and it is not small. It shows that he’s increasingly detached from reality. Everyone knows if Biden or Harris did that it would be media mayhem. He’s not ok, and you can’t ignore it anymore.

— Brian Schatz (@brianschatz) October 15, 2024

Tuesday’s incident came just days after Harris, 59, released her medical records, and challenged Trump to do the same.

At 78, he is the oldest person to run for US president – after incumbent Democratic President Joe Biden, 81, was forced out of the race amid concerns about his age.

In a letter released on Sunday (AEDT), a US military doctor gave Harris a clean bill of health and said she “possesses the physical and mental resiliency” required to serve as president.

Trump has consistently refused to release his medical records.

Most details known about his health are from a physician’s report nearly seven years ago. It revealed he was overweight, had high cholesterol and suffered from rosacea, a skin condition that causes face redness.

Trump lashed the “desperate request” for his medical records in posts on his Truth Social platform from about 1am on Tuesday (local time).

“I have already provided them, many times, including quite recently, and they were flawless,” he said, misleadingly.

He also took aim at Harris’s health report, claiming her allergies could prevent her from serving as US president.

“I have just seen Kamala’s Report, and it is not good,” he wrote.

“She also has ‘allergic rhinitis and allergic conjunctivitis’, a very messy and dangerous situation. These are deeply serious conditions that clearly impact her functioning. Maybe that is why she can’t answer even the simplest of questions asked by 60 Minutes, and others.”

Allergic rhinitis is more commonly called hay fever, while allergic conjunctivitis is a related eye condition.