An Associated Press reporter witnessed a man storm the stage at the Chautauqua Institution on Friday (Saturday morning AEST) and begin punching or stabbing Rushdie as he was being introduced.
The 75-year-old author was pushed or fell to the floor, and the man was restrained.
Rushdie was quickly surrounded by a small group of people who held up his legs, presumably to send more blood to his chest.
His condition was not immediately known.
Hundreds of people in the audience gasped at the sight of the attack and were then evacuated.
Rushdie’s book The Satanic Verses has been banned in Iran since 1988, as many Muslims consider it to be blasphemous. A year later, Iran’s late leader Ayatollah Ruhollah Khomeini issued a fatwa, or edict, calling for Rushdie’s death.
A bounty of more than $US3 million ($4.22 million) has also been offered for anyone who kills Rushdie.
Iran’s government has long since distanced itself from Khomeini’s decree, but anti-Rushdie sentiment has lingered. In 2012, a semi-official Iranian religious foundation raised the bounty for Rushdie from $US2.8 million to $US3.3 million ($3.94 million to $4.65 million).
Rushdie dismissed that threat at the time, saying there was “no evidence” of people being interested in the reward.
That year, Rushdie published a memoir, Joseph Anton, about the fatwa. The title came from the pseudonym Rushdie had used while in hiding.
Rushdie rose to prominence with his Booker Prize-winning 1981 novel Midnight’s Children, but his name became known around the world after The Satanic Verses.
The Chautauqua Institution, about 120 kilometres southwest of Buffalo in a rural corner of New York, is known for its summertime lecture series. Rushdie has spoken there before.
