Top Bollywood star Shah Rukh Khan is among those who have been threatened in recent months.
Mumbai gangsters have returned to targeting <a href="http://www.theguardian.com/film/bollywood" rel="nofollow" target="_blank">Bollywood</a> celebrities in an effort to find a "new business model", police in India's commercial capital say.
A key aim of the threats to top stars is boosting the gangsters' credibility when trying to extort cash from less well-known - but often wealthier - targets.
In recent years local criminals have largely abandoned the nation's high-profile, high-octane film industry for less risky ventures in sectors such as real estate and finance.
But last month Mahesh Bhatt, a well known director, escaped a third attempt on his life by gunmen in the city hired by a gang leader living overseas.
Bhatt told the Times of <a href="http://www.theguardian.com/world/india" rel="nofollow" target="_blank">India</a> newspaper that "the film fraternity must stand shoulder to shoulder with Mumbai police and fight the menace of organised crime".
"If we try and buy peace by giving in to their demands, we would be giving a blood transfusion to this monster which is taking its last gasp," the director said.
Top Bollywood stars such as Shah Rukh Khan and Salman Khan, idolised by tens of millions in south Asia and beyond, are among those who have been threatened in recent months.
"The threats serve a purpose. The target is not the celebrity as such. The aim is to make other people think that if the extortionist is prepared to go after such high-profile people then they had better pay up and keep quiet," a senior police officer dealing with crime in Mumbai said.
Though India's economic boom has faltered in recent years, two decades of growth have generated vast amounts of money and thus, police say, many wealthy individuals who are prime targets for extortion.
Investigators have intercepted communications indicating that gunmen have been told not to hurt top film stars but simply to scare them.
"When there was a serious attempt on one star's life, we were listening to the instructions to the gunmen and heard him being told: "This time, shoot this one properly," the senior officer said.
Targets appear to have also been chosen to generate maximum attention. Anything involving top stars will be widely reported across India's raucous media, while Bhatt, the director, is known for speaking out on a range of issues, and particularly links between the film industry and criminals.
For many years Bollywood, which produces more than 350 films each year, generating an estimated $50bn-plus revenue, has been <a href="http://www.ibtimes.com/bollywood-100-how-big-indias-mammoth-film-industry-1236299" rel="nofollow" target="_blank">almost synonymous with</a> the notorious gangs of Mumbai, a city of more than 20 million people.
The relationship has long been a tempestuous one. Black money flowed into often high-risk productions which would otherwise have not received funding while some actors and gang members became close.
Wanted criminals were regular guests at big Bollywood weddings and other functions.
"In the 1990s they were everywhere - funding, planting their people inside, even deciding casting," said Hussain Zaidi, <a href="http://www.penguinbooksindia.com/en/content/my-name-abu-salem" rel="nofollow" target="_blank">one of India's best-known crime reporters</a> and an expert on the Mumbai underworld.
At the end of the decade, a series of directors and producers were attacked and several killed, while many more secretly paid large sums or handed over lucrative rights to criminals.
Now big corporations are more likely to back major productions than underworld dons. New legal structures, based on practices elsewhere in the world, also protect actors and directors from extortionists.
Previously, criminals regularly demanded that producers gave them rights to overseas distribution. Now rights are held by anonymous trusts or companies, which cannot be intimidated.
The gangs themselves are also much weaker. Many suffered significant losses at the beginning of the last decade from specially formed armed police units that shot hundreds of suspected members on sight.
<a href="http://www.theguardian.com/world/2011/mar/06/mumbai-police-encounter-squad-return" rel="nofollow" target="_blank">These "encounter specialists" were later disbanded but not before many of the most notorious gang leaders were forced into exile or killed.</a>
Zaidi, the crime writer, said that most of those involved in the recent threats to Bollywood celebrities were not major underworld figures.
"All the big guys have pretty much retired so these are just desperadoes trying to establish themselves and cash in on the fear factor," he told the Guardian.
Police say the threats have come from a gang leader called Ravi Pujari, who they believe is now based either in Australia or the west coast of the US.
Many top criminals once based in the Gulf have now moved further afield and use digital communications technology to disguise their location when making threats.
Pujari was born and raised in Mumbai's northern suburb of Andheri and started his criminal career with the gang of an established mafia boss. Wanted in India on charges relating to more than 30 cases of extortion, the 43-year-old high school dropout had been "below the radar" until the recent series of threats to Bollywood figures, police officers said.
"One possibility may be that with economic growth picking up, developers are more active and he thinks now is a time to make some money," one told the Guardian.
Another suggested that the gangsters were "in search of a new business model".
Dawood Ibrahim, suspected of masterminding a devastating bombing campaign in Mumbai in 1993, remains the most-wanted Indian underworld figure. Indian police believe Ibrahim fled Mumbai for Dubai before finding a safe haven in Karachi, the port city in Pakistan.
Last week Rajnath Singh, the home minister, said the fugitive criminal was hiding somewhere on the neighbouring state's border with Afghanistan.
<a href="http://www.dailymail.co.uk/indiahome/indianews/article-2139817/Gangs-Bollywood-Slew-new-films-attempt-gangster-flick-level.html" rel="nofollow" target="_blank">The success of gangster films such as Satya, Company, Shootout At Lokhandwala, Gangs of Wasseypur and Once Upon A Time In Mumbaai</a> testifies to the enduring fascination of the underworld for Indians.
In many cases involving Bollywood and the gangs, life has a habit of imitating life as well as vice versa.
Abu Salem, described as "one of the most colourful gangsters in the pantheon" by local media, is reported to be writing his memoirs in prison. He believes his life would <a href="http://www.mumbaimirror.com/mumbai/cover-story/Two-jail-mates-helping-Salem-write-his-story/articleshow/45235380.cms" rel="nofollow" target="_blank">make a great film</a>, said the Mumbai Mirror tabloid.
This article was originally published on <a href="http://www.theguardian.com/cities" rel="nofollow" target="_blank">The Guardian</a>.