President Joe Biden is "fine" after tripping and falling over at an event in Colorado, White House officials say.

He stumbled on a sandbag while handing out diplomas at a graduation ceremony for the US Air Force Academy.

Mr Biden, who is the nation's oldest serving president at 80, was helped back onto his feet and appeared to be unhurt after Thursday's fall.

"I got sandbagged!" the president joked to reporters as he arrived back at the White House that evening.

He had been standing for about an hour and a half to shake hands with each of the 921 graduating cadets.

Footage shows Mr Biden appearing to point at one of two sandbags used to prop up his teleprompter as he was helped up by an Air Force official and two members of his Secret Service detail.

He was seen walking back to his seat unassisted and later jogging back to his motorcade when the ceremony ended.

"There was a sandbag on stage while he was shaking hands," White House communications director Ben LaBolt wrote on Twitter. "He's fine."

White House press secretary Karine Jean-Pierre said Mr Biden had boarded the plane flashing "a big smile", although one reporter noted that he did not take questions before the flight.

Critics have said Mr Biden is too old to run for a second term as president.

Recent polls suggest a majority of US voters are concerned about his advanced age. He would be 82 at the start of a second term if he wins.

This fall, in addition to previous stumbles from his bicycle and on the way up the Air Force One stairs, could add to those concerns.

Former President Donald Trump, the Republican frontrunner to face Mr Biden in the 2024 White House election, reacted to the incident from a campaign event in Iowa, saying "the whole thing is crazy".

"I hope he wasn't hurt," said Mr Trump, 76, who has often poked fun at Mr Biden's age. "That's not inspiring."

"You got to be careful about that because you don't - you don't want that. Even if you have to tip toe down the ramp," added Mr Trump, apparently referring to his own careful walk off a stage that made headlines in 2020.

He said at the time that the ramp at the US Military Academy in West Point, New York, was slippery, and brushed aside the ensuing media questions about his own health as fake news.

Florida Governor Ron DeSantis, another 2024 contender for the Republican nomination, also reacted to the fall during a campaign event in New Hampshire: "We hope and wish Joe Biden a swift recovery from any injuries he may have sustained.

"But we also wish the United States of America a swift recovery from the injuries it has sustained because of Joe Biden and his policies."

Mr Biden's last physical examination took place in February.

White House physician Dr Kevin O'Connor wrote at the time: "The President remains fit for duty, and fully executes all of his responsibilities without any exemptions or accommodations."

Dr O'Connor added that Mr Biden walks with a "stiffened gait", largely caused by wear and tear on his spine and nerve damage in his feet, but that his condition was unchanged from a previous physical in November 2021.

Mr Biden is hardly the first commander-in-chief to lose his footing in front of the cameras.

President Barack Obama tripped walking up stairs at a 2012 event, while President Gerald Ford fell down the stairs of Air Force One in 1975.