Democratic nominee Hillary Clinton's illness while attending the September 11 ceremony in New York drew reactions from commentators, journalists and activists.

Clinton left about 90 minutes into the ground zero ceremony after feeling "overheated," her campaign said. Video showed her knees buckling as three people helped the 68-year-old Democrat into a van in the muggy heat. Later in the day, she said she was "feeling great" as she walked to a vehicle.

Donald Trump, who has repeatedly questioned whether Clinton is physically fit to be president, was also at the ceremony for a time and left after she did. Asked about the incident, the Republican nominee said only: "I don't know anything about it".

Several hours later, Clinton's campaign revealed that she had been diagnosed with pneumonia on Friday and advised to rest.

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