The United States on Friday imposed sanctions on an Iranian foundation accused of issuing a multimillion-dollar bounty for killing British-American author Salman Rushdie, who was attacked at a literary event in August.

In a statement, the US Treasury Department announced sanctions against the 15 Khordad Foundation and classified it as a Specially Designated Global Terrorist. The sanctions freeze any US-based assets the organisation may have and prevents Americans from carrying out transactions with it.

“Since [Iran’s late Supreme Leader] Ayatollah Ruhollah Khomeini’s order pronouncing a death sentence on Rushdie in February 1989, 15 Khordad Foundation has committed millions of dollars to anyone willing to carry out this heinous act,” the treasury department said in the statement.

In 1989, Khomeini had issued a fatwa, or religious edict, calling for Rushdie’s assassination after his book, The Satanic Verses, was published. Some Muslims consider the book blasphemous. The Iranian government had later distanced itself from the call to kill Rushdie, who had spent years in hiding after the edict.

On August 12, Rushdie was stabbed in the neck and abdomen as he was being introduced at the Chautauqua Institution in New York state. The 75-year-old has lost sight in one eye and the use of one hand, his agent Andrew Wylie had told Spanish newspaper El Pais on October 22.

“This act of violence, which has been praised by the Iranian regime, is appalling,” said Brian Nelson, the treasury’s under secretary for terrorism and financial intelligence, in Friday’s statement.

In the statement, the Treasury Department accused the 15 Khordad Foundation of increasing the bounty on Rushdie to $3.3 million in 2012.

“The United States will not waver in its determination to stand up to threats posed by Iranian authorities against the universal rights of freedom of expression, freedom of religion or belief, and freedom of the press,” Nelson added.

Rushdie’s attacker, Hadi Matar, has been incarcerated after pleading not guilty to attempted murder and assault. He is being held without bail in a western New York jail.

In an interview with The New York Post in August, Matar had said he does not like Rushdie and described Khomeini as “a great person”.

Matar added that he had only read “a couple of pages” of The Satanic Verses but had watched lectures by the author online.