Salman Rushdie, whose writing led to death threats in the 1980s, was stabbed in the neck and abdomen by a man who rushed the stage as the author was about to give a lecture in western New York.
He is on a ventilator and may lose an eye, according to the New York Times, and sustained nerve damage to his arm and damage to his liver.
The Indian-British author, 75, was attacked on Friday onstage at the Chautauqua Institution.
Police identified the attacker as Hadi Matar, 24, of Fairview, New Jersey. He has been taken into custody.
Witnesses reported Rushdie falling to the floor when the man attacked him, and was then surrounded by a small group of people who held up his legs, seemingly to send more blood to his upper body, as the attacker was restrained.
According to the NYT, Rushdie’s agent Andrew Wylie said he is on a ventilator and unable to speak.
Wylie added the news was “not good” and the author will “likely lose one eye”.
He said the nerves in Rushdie’s arm were severed in the attack and his liver was “stabbed and damaged”.
Rabbi Charles Savenor was among the hundreds of people in the audience. Amid gasps, spectators were ushered outside.
“This guy ran on to platform and started pounding on Mr Rushdie. At first you’re like, ‘What’s going on?’ And then it became abundantly clear in a few seconds that he was being beaten,” Savenor said. He said the attack lasted about 20 seconds.
Major Eugene Staniszweski of New York State Police said late on Friday: “Earlier today at approximately 10.47am, guest speaker Salman Rushdie, aged 75, and Ralph Henry Reese, age 73, had just arrived on stage at the institution.
“Shortly thereafter, the suspect jumped on to the stage and attacked Mr Rushdie, stabbing him at least once in the neck and at least once in the abdomen.
“Several members of the staff at the institution and audience members rushed the suspect and took him to the ground, and shortly thereafter, a trooper who was at the institution took the suspect into custody with the assistance of a Chautauqua County Sheriff’s deputy.
“Mr Rushdie was provided medical treatment by a doctor who was in the audience until EMS arrived on scene.
“Mr Rushdie was airlifted to a local trauma centre and is still currently undergoing surgery.”
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 and issued a fatwa, calling for Rushdie’s execution.
A bounty of over $3 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 $2.8 million to $3.3 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 55 miles southwest of Buffalo in a rural corner of New York, is known for its summertime lecture series. Rushdie has spoken there before.