Author Sir Salman Rushdie's controversial video address to the Jaipur Literary Festival in India has been cancelled, its organiser says.
Sanjoy Roy said nearly 30 Muslim activists had tried to enter the venue and police had told him large crowds were gathering at city parks to march.
Sir Salman tweeted that the threat of violence had "stifled free speech".
Many Muslims regard Sir Salman's book, The Satanic Verses, as blasphemous and it is banned in India.
The video-link had been organised after Sir Salman withdrew from attending the festival, saying that sources had told him of an assassination threat.
Sir Salman lived in hiding for many years after Iran's Ayatollah Khomeini issued a fatwa calling for his execution.
Indian Islamist hardliners had demanded Mr Rushdie be denied a visa because of The Satanic Verses.
'Pushed to the wall'
Announcing the cancellation of the video-link, an emotional Sanjoy Roy said: "We have been pushed to the wall... Earlier today, a number of organisations came to us and threatened violence.
"Even now as we speak, we have been informed by the police that large crowds are gathering across the city parks and marching towards the Diggi Palace [festival venue]," he said.
Ram Pratap Singh, owner of the Diggi Palace, said: "I have taken a decision not to allow the video-link to go ahead on advice from the police.
"There are a large number of people who are averse to this video-link and they are actually inside the property... they have threatened violence if the video-link takes place," he said.
"This is unfortunate but necessary to avoid harm to the property, to all of you, to my children and all the youngsters who are here," he added.
Sir Salman later tweeted: "Threat of violence by Muslim groups stifled free speech today. In a true democracy all get to speak, not just the ones making threats."
The protests on Tuesday afternoon were led by All India Milli Council leader, Paiker Farukh. He has alleged that "the festival is trying to portray author Salman Rushdie as a hero".
"We have every right to protest in a democratic manner and if the Muslim population of Jaipur comes out in protest, you cannot prevent us. You cannot take us for a ride... we are not fools," Mr Farukh told journalists outside the Diggi Palace.
The cancellation of the event sparked angry reactions on Twitter.
"It's official - we have buckled. No Salman Rushdie video-link. India officially proves to the world that it lacks freedom of speech," tweeted author Shobhaa De.
"Why is the Rajasthan government scared of Salman Rushdie? Even just a video Rushdie from far away? Shame on the chief minister," columnist Tavleen Singh tweeted.
Author-publisher Tarun Tejpal wrote: "It's a triumph of bigotry but the battle against this will go on."
Earlier on Tuesday, Mr Roy told reporters that Sir Salman would address the festival for an hour via video conference.
The author was to speak on his Booker-prize winning novel Midnight's Children and his "life and times", Mr Roy said.
Tuesday is the final day of the five-day festival. It has attracted more than 70,000 visitors, along with leading writers such as Tom Stoppard, Michael Ondaatje and David Hare.
Police in Jaipur say they are investigating whether Mr Roy and four authors broke the law by reading excerpts from The Satanic Verses at the Jaipur event.
Earlier, Sir Salman accused authorities in Rajasthan of giving "false intelligence information" of the threat to his life.
Rajasthan authorities said Sir Salman's allegation was "baseless" and that they had "confirmed information" about a threat to his life.
Festival organisers said on Tuesday that they had got information from the Rajasthan government "and other sources" about a threat to Sir Salman's life and conveyed it to the author.
Salman Rushdie was born in India but is a British citizen and has lived in the UK for most of his life.
In recent years he has made many private visits to India and attended the Jaipur Literary Festival in 2007.