Author Salman Rushdie, whose writing led to death threats, has been stabbed in the neck while on stage at an event in New York state.
He was about to give a lecture when a man stormed the stage at the Chautauqua Institution.
He fell to the floor when the suspect attacked him. The suspect was restrained and is now in custody.
A video posted online showed a number of people rushing on stage in the aftermath.
On stage there were two yellow chairs, a table and a rug.
Mr Rushdie has been taken to hospital by helicopter, but his condition is not yet known.
His agent said he is undergoing surgery.
'It was very quick'
State police said in a statement they are "investigating an attack on author Salman Rushdie prior to a speaking event at the Chautauqua Institution in Chautauqua, NY".
"At about 11am, a male suspect ran up onto the stage and attacked Rushdie and an interviewer. Rushdie suffered an apparent stab wound to the neck, and was transported by helicopter to an area hospital."
They added: "The interviewer suffered a minor head injury.
"A State Trooper assigned to the event immediately took the suspect into custody. The Chautauqua County Sheriff's Office assisted at the scene."
Witness Julia Mineeva-Braun said Mr Rushdie was being introduced when "all of a sudden from the left-hand side of the stage a short man, (dressed) all in black, ran out and he approached Mr Rushdie".
"It was very quick... we thought he was fixing his microphone and then we saw the knife.
"He starting stabbing him in the neck first… and Mr Rushdie got up and started running.
"After that, people in the audience got up on stage and pinned the attacker down. It's hard to believe. We're still in shock."
New York Governor Kathy Hochul said a state police officer saved the author's life and that of the moderator, who she said was also hurt.
Ms Hochul added: "He is alive, he has been airlifted to safety.
"But here is an individual who has spent decades speaking truth to power, someone who's been out there unafraid, despite the threats that have followed him his entire adult life."
Rushdie's book, The Satanic Verses, has been banned in Iran since 1988 - as many Muslims consider it to be blasphemous.
A year after that, Iran's late leader Ayatollah Ruhollah Khomeini issued a fatwa, or edict, calling for Rushdie's death.
The Middle Eastern country has also offered a bounty of more than US$3m for anyone who kills Rushdie.
The 75-year-old Indian-born author also has British and US citizenship.
Speaking in 2015, Rushdie said: "If you're a free expression organisation, if you believe in the value of free speech, then you must believe in the value of free speech that you don't like.
"If you only defend free speech that conforms to your own moral framework that's what is normally called censorship."