The incident occurred as Trump was defending his recent claim that he had witnessed thousands of Muslims cheering in New Jersey on September 11, 2001, as the World Trade Center collapsed.
The assertion has since been fact-checked and discredited by law enforcement and government officials who were in New Jersey in the days and weeks following the terrorist attacks.
On Tuesday, Trump berated New York Times investigative reporter Serge Kovaleski for his recent recollection of an article he had written a few days after the 9/11 attacks.
"Now, the poor guy - you've got to see this guy, 'Ah, I don't know what I said! I don't remember!'" Trump, 69, said as he jerked his arms in front of his body.
More From This Section
The gesture was all the more personal because Kovaleski covered Trump while reporting for another US daily between 1987 and 1993, a tumultuous period for Trump in which he struggled through several financial setbacks.
"The sad part about it is, it didn't in the slightest bit jar or surprise me that Donald Trump would do something this low-rent, given his track record," Kovaleski was quoted as saying by Washington Post.
According to the campaign official, Trump "was merely emphasising the uncertainty of the statement provided by the reporter in regards to his article."
Trump was widely criticised on the social media for his behaviour.
This is not the first time Trump has been panned for apparently mocking a person's physical disability.
In July, Trump lashed out at columnists Jonah Goldberg and Charles Krauthammer. Krauthammer had called the candidate a "rodeo clown."
Krauthammer is paralysed from the waist down.
The New York Times also issued a terse statement.
"We think it's outrageous that he would ridicule the appearance of one of our reporters," a spokesman for the Times said.