India's Rajasthan state continues to be on alert following the beheading of a Hindu man by two Muslim men.
Chief Minister Ashok Gehlot has appealed for calm and promised to take strict action against the attackers.
The victim, a tailor named Kanhaiya Lal, was killed in Udaipur district in north India on Tuesday by the men, who filmed the act and posted it online.
They said the act was in response to his support for a politician's dividing remarks about the Prophet Muhammad.
The National Investigative Agency - India's top anti-terrorism agency - is carrying out a probe. A senior police officer told reporters that the police had found early evidence that one of the accused men had links with a group in Pakistan.
Islamabad, however, has denied such reports, calling them "mischievous".
The BBC's Nitin Srivastava, who's in Udaipur, said the streets were empty and communities were living in fear of religious violence.
He added that there was heavy deployment of police forces across the city and senior officers were constantly appealing for peace.
Most people were unprepared for a curfew, with many now struggling to get hold of even basic rations.
"Daily wagers are worst affected," said Mukesh Gardiya, a local man. "All that's happened is a big shock."
The government has suspended internet services and banned large gatherings. Police have arrested the two men, who had identified themselves in the video.
In another video, the accused boasted about the murder and also issued threats to Prime Minister Narendra Modi while brandishing cleavers. A top Rajasthan police official asked media outlets not to broadcast the video of the murder as it was "too grisly to watch".
The men posed as customers to enter Kanhaiya Lal's shop, and attacked him while he was taking their measurements.
The victim had allegedly put up a social media post supporting former Bharatiya Janata Party (BJP) spokesperson Nupur Sharma, who made controversial comments about the Prophet Muhammad last month.
Her comments sparked a diplomatic row with several Islamic countries registering strong protests with India. The BJP subsequently suspended Ms Sharma from the party.
The controversy also led to religious protests in India which turned violent after demonstrators threw stones and damaged public property.
Three weeks before his murder, Kanhaiya Lal had been arrested by the police for allegedly hurting religious feelings, the Indian Express reported. He had asked for police protection after his release, citing threats to his life.
The police then called some Hindus and Muslims for a peace meeting, after which Kanhaiya Lal said he didn't "need any more action against any one", a police official told the newspaper.
The incident has been condemned by prominent politicians across party lines in India.
Former Rajasthan chief minister Vasundhara Raje, who belongs to the BJP, blamed Mr Gehlot's Congress party government, saying "a situation of communal frenzy and violence has arisen in the state".
Some BJP leaders have said they will march in the national capital Delhi to protest against the killing.
Congress leader Rahul Gandhi said he was "deeply shocked" by the murder and called for immediate punishment for the attackers.
Some prominent Muslim organisations have also condemned the murder. The All India Muslim Personal Law Board called the incident "highly condemnable", adding that it was against both Indian law as well as Islamic strictures.
"Nobody can be allowed to take the law into their hands and declaring someone a criminal and then murdering them is a highly condemnable act," the board said in a statement.