The suspected assailant of Salman Rushdie pleaded not guilty on Thursday to attempted murder and assault charges at a brief court hearing in upstate New York.

Speaking through his lawyer, Hadi Matar, 24, reiterated his plea of not guilty to charges he faces for allegedly storming the stage at a literary event last week and stabbing the British novelist several times in the neck and abdomen.

Thursday's appearance at a court in Chautauqua County followed a grand jury indictment, according to county prosecutors.

The judge ordered Matar remain detained without bail. He is next scheduled to appear in court on September 7.

His head bowed, Matar wore a black and white striped prison outfit with orange crocs at the hearing that drew numerous reporters.

Following last Friday's attack, Rushdie was air-lifted to a nearby hospital for emergency surgery.

His condition remains serious but the 75-year-old has shown signs of improvement, and he has been taken off a ventilator.

The prize-winning writer spent years under police protection after Iranian leaders called for his killing over his portrayal of Islam and the Prophet Mohammed in his novel 1988 "The Satanic Verses."

He was about to be interviewed as part of a lecture series at the Chautauqua Institution when a man rushed the stage and stabbed him repeatedly in the neck and abdomen.

Matar was wrestled to the ground by staff and audience members at the lecture, before police took him into custody.

Police and prosecutors have provided scant information about Matar's background or the possible motivation behind the attack.

Matar's family appears to come from the village of Yaroun in southern Lebanon, though he was born in the United States, according to a Lebanese official.

Rushdie, who was born in India in 1947, moved to New York two decades ago and became a US citizen in 2016.

Despite the continued threat to his life, he was increasingly seen in public - often without noticeable security.

In an interview given to Germany's Stern magazine days before Friday's attack, he had described how his life had resumed a degree of normality following his relocation from Britain.

Iran this week denied any link with Rushdie's attacker but blamed the writer himself for "insulting" Islam in "The Satanic Verses".

"By insulting the sacred matters of Islam... Salman Rushdie has exposed himself to the anger and rage of the people, said Iranian foreign ministry spokesman Nasser Kanani said.

In Washington, US State Department spokesman Ned Price described Iran's stance as "despicable."