Sir Salman Rushdie was stabbed about 12 times – including in the face and neck, a US district attorney’s office has said.
One of the wounds in the facial area caused a puncture to Sir Salman’s eye, the Chautauqua County District Attorney’s Office said.
Another, to the abdomen, caused a puncture of the author’s liver.
There were also multiple further stab wounds to the abdomen and chest area.
The 75-year-old was airlifted to hospital and underwent hours of surgery following the attack ahead of a lecture he was due to give in New York state on Friday afternoon.
Earlier on Saturday, the suspect pleaded not guilty to attempted murder.
Hadi Matar, 24, appeared in court wearing a black and white jumpsuit and a white face mask, his hands cuffed in front of him.
The Indian-born British writer, Sir Salman, was being introduced at the Chautauqua Institution when a man stormed the stage and began stabbing him.
He fell to the floor as the suspect was pinned down by audience members and staff.
Witness Julia Mineeva Braun told Sky News a man had appeared “all of a sudden from the left-hand side of the stage… (dressed) all in black.
“It was very quick… we thought he was fixing his microphone, and then we saw the knife. He started stabbing him in the neck first… and Mr Rushdie got up and started running. We’re still in shock.”
Sir Salman, who lives in New York City and became an American citizen in 2016, was due to speak to Henry Reese, from the City of Asylum organisation, a residency programme for writers living in exile under threat of persecution.
They were expected to discuss America’s role as an asylum for writers and other artists in exile and as a home for freedom of creative expression.
His fourth book, The Satanic Verses, was banned in 1988 in a number of countries with large Muslim populations, including Iran, after it was considered by some to contain blasphemous passages.
In 1989, Iran’s then leader Ayatollah Ruhollah Khomeini issued a fatwa, or edict, calling for Sir Salman’s death.
The author lived in exile for years, but told a German magazine earlier this month he believed his life was “very normal nowadays”.
Prime ministerial hopeful Rishi Sunak’s has called for Iran’s Revolutionary Guard to be officially designated a terrorist organisation following the brutal attack.
He told the Sunday Telegraph the stabbing should be a “wake-up call for the West”.
Iranians reacted with both praise and concern over the attack.
‘I am happy he was attacked’
Reza Amiri, a 27-year-old deliveryman in Tehran, told the Associated Press: “I don’t know Salman Rushdie, but I am happy to hear that he was attacked since he insulted Islam.
“This is the fate for anybody who insults sanctities.”
Others, however, expressed fears that Iran could become even more cut off from the world as tensions remain high over its tattered nuclear deal.
“I feel those who did it are trying to isolate Iran,” said Mahshid Barati, a 39-year-old geography teacher. “This will negatively affect relations with many – even Russia and China.”