A grand jury has indicted the man suspected of stabbing Salman Rushdie as the acclaimed author prepared to give a talk in western New York, county prosecutors have said.

Hadi Matar, 24, of Fairview, New Jersey, is scheduled to appear on the charges at an afternoon court hearing in Chautauqua County.

Matar was arrested on August 12 after he allegedly rushed the stage at the Chautauqua Institution, stabbing Sir Salman multiple times in front of a horrified crowd.

Initial charges were filed the next day, when Matar’s court-appointed lawyer entered a not guilty plea on his behalf. The prosecutor’s office did not immediately release the new charges.

Sir Salman, 75, is receiving treatment in a Pennsylvania hospital for severe wounds.

His literary agent, Andrew Wylie, has said Sir Salman has a damaged liver and severed nerves in an arm, and could lose an eye.

Sir Salman’s life has been in jeopardy since 1989 when Iran’s supreme leader at the time, Grand Ayatollah Ruhollah Khomeini, issued an edict demanding his death over his novel The Satanic Verses, which was viewed as blasphemous by many Muslims.

A semi-official Iranian foundation had posted a bounty of over three million US dollars (£2.5 million).

Chautauqua County District Attorney Jason Schmidt called the attack “pre-planned”.

The author had just taken to the stage at the lakeside retreat for a discussion of protections for writers in exile and freedom of expression when Matar allegedly jumped onstage.

Henry Reese, 73, the cofounder of Pittsburgh’s City of Asylum, was onstage with Sir Salman and suffered a gash to his forehead, bruising and other minor injuries.