The Indian defence minister has said that two week-end bomb attacks on cinemas in the capital Delhi appeared to be the work of "terrorists".
The cinema blasts occurred within minutes of each other
Pranab Mukherjee warned of "stern action" against the perpetrators.
One person died and at least 49 others were injured in the bomb attacks on Sunday. No-one has claimed responsibility for the blasts.
Police initially thought the attacks may were carried out by Sikhs, but they now suspect Islamic militants.
"It is not the work of some agitated people. It is the work of some organised terrorist group who are trying to take advantage of ruffled sentiments of a particular community," Mr Mukherjee said.
The film, Jo Bole So Nihaal (Blessed is the One), is considered offensive by some Sikhs who say that it denigrates the Sikh faith.
"We don't think the attack was to protest the film's screening as we first thought," a senior Delhi police official told the AFP news agency.
"The blasts are not the work of an amateur group. Islamic rebel groups often use plastic explosives like those used on Sunday," he said.
"Plastic explosives without metal shrapnel need a lot of heat to set them off and are favourites with the Lashkar-e-Toiba and Jaish-e-Mohammad," he added. "These explosives can go undetected by metal detectors."
Lashkar-e-Toiba and Jaish-e-Mohammad were blamed for an attack on the Indian parliament in 2001.
Cities across India remain on high alert following the blasts.
The West Bengal chief minister said that the film had been withdrawn from Calcutta as a "precautionary measure", while more than half of the 20 cinemas in India's entertainment capital, Mumbai (Bombay) have temporarily stopped showing it.
The twin blasts in Delhi's western Karol Bagh district occurred within minutes of each other, causing panic among hundreds of cinema goers.
Eyewitness accounts describe one explosion tearing through the toilets of the Satyam cinema hall.
The second blast was suspected to be under the front seats near the screen at the nearby Liberty cinema.
Authorities began to shut all cinema halls across the city following the blasts.
The film was withdrawn from theatres across the largely Sikh state of Punjab last week, following protests.
It was showing for the first time in Delhi at the weekend.
The powerful body which administers historic Sikh shrines, the Shiromani Gurudwara Prabandhak Committee (SGPC), led calls for it to be withdrawn.
Its president, Bibi Jagir Kaur, condemned the attacks in Delhi, saying they had been carried out by nefarious elements seeking to malign the Sikh community.
But Ms Kaur, who had called for a world-wide ban on the film, blamed the government for failing to take timely action to stop the screening of the film.
In December 2004, a play which led to violent protests among the Sikh community in Birmingham, UK, had its run cancelled by the city's Repertory Theatre.
Did you witness the blasts in Delhi? Send us your comments and experiences using the form below.
It appears from your report that the film is perceived by many Sikhs as being disrespectful of their religion and prominent community leaders previously called for a world-wide ban of the film. As an ardent supporter of artistic freedom although I strongly disapprove of violence in such matters I would urge the film makers to show responsibility not to offend the practitioners of any faith.
Riaz Ahmed, St Albans, Herts, UK
To Raj Chatha, England One person is dead officially from the blast. Will you have the same opinion if that person were your friend/relative?
Sikhs are as much a victim of this crime as the non-Sikhs. Both the cinemas are located in areas where a lot of Sikhs reside. People should keep this in mind and keep things in perspective before reacting violently. Hopefully we have all learnt from the riots of 84 and Gujarat and do not need any more blood baths in the name of religion.
Jaswinder, Boston, USA
Once again it seems the Sikh faith is the most intolerant in the world, with ANY criticism leading to bombing, riots or other types of violence.
Adam, London, UK
I think this clearly demonstrates that the violent elements in every culture represent a global danger because they act as they do regardless of the tolerance and justice the religion underlying it heralds as truth.
Dave, Boston, MA
I strongly condemn the acts of the militants who did such a shameful act.. I am sure its not done by any true Sikh.. its definitely a nefarious activity of some anti-social elements who do not belong to any religion.
Prateek Sharma, Jalandhar, Punjab
I wonder what fault it was of the person who died. Sikhs should realize that the bomb blast would probably denigrate their faith more than the movie ever could. They should distance themselves from this action strongly. The Indian government has to make sure that riots, like that after Indira Gandhi's death, do not ensue. Wanton killings on Delhi's streets of a particular community isn't acceptable.
Kunal Shenoy, San Jose, USA
The Sikhs have been a peaceful and progressive community in India for many years. Terrorists have taken this opportunity to defame them. Sikhism is a tolerant religion and they would not resort to such activities as this would bring memories of the problems in the 80's in people's minds.
Ramesh Sharma, New York
The feelings of Sikhs might have been hurt, but the situation should have been dealt with law. If the culprits are proved to be Sikhs, this could lead to the events happened during post Indira assassination.
Atri, Hyderabad, India
The Sikhs warned all parties involved to change the name of the film or not to screen it but it all fell on deaf ears, no one took much notice. The Sikhs had no choice but to take this measure for sake of Sikhism.
Raj Chatha, England
Though I was not a witness to the blast, my brother and I were at a multiplex which was screening 'Jo Bole So Nihal', and we had the tickets for 'Star Wars Ep. III'. There was a little panic at the multiplex and you could see nearly everyone speaking on their cell phones. Even I received a call from my parents who are in the Middle East telling us to go home immediately. Subsequently all the shows were cancelled and our money refunded. On our way home we could see police barricades at strategic points where 'suspicious' characters were being halted and interrogated.
Mohsin Arabi, New Delhi, India
This is another opportunity for someone to easily blemish the name of the Sikhs. Lately the majority law abiding Sikhs have become an easy target and after Birmingham this will just add fuel to the fire to people who have a glance view on the subject. Every Sikh will condemn what happened as it will probably turn out that this outrage was not done by Sikhs but by non Sikh parties of a malign purpose.
Manjit Rekhi, Gravesend, UK
I wonder when will they stop singers like Jazzy B, Sukhbinder, Mika, Daler from showing half naked ladies in Punjabi songs. I thought my religion is most youngest and modern religion of the world. I was expecting it to be full of tolerance and flexibility. Shame on such incidences. Whether Sikhs have blasted or not but why to oppose such things. Tolerance is the preacher of the religion.
Harpreet Singh, Edinburgh UK
Terrorists just want an excuse to destabilise the country. They could be anybody, not necessarily Sikh militants. Otherwise why would anyone want to kill people just for some controversial movie?
It's just a movie title...it's silly that some idiots are using that as a pretext to carry out such dastardly acts...
Sunder, Burlington, Vermont
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