Police said 32 people were detained for trying to convert people to Christianity in the central Indian state of Madhya Pradesh late Thursday, with a leading Catholic association condemning the accusations as "laughable".
When a group of priests went to the police station to enquire about the detentions, their parked car was torched, allegedly by a mob belonging to a right-wing Hindu group, said Theodore Mascarenhas, secretary general of the Catholic Bishops' Conference of India.
The news comes as India's Christian minority sounds the alarm over a recent rise in attacks on churches and members of the faith, blaming the violence on Hindu hardliners, who they say have become emboldened since Prime Minister Narendra Modi's right-wing government swept to power in 2014.
Mascarenhas said 32 Catholics, including two priests, were detained while "conducting a routine Christmas carol singing programme".
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"The charge of conversion on which the priests and seminarians (were) detained is frivolous and laughable," Mascarenhas said in a statement on Friday.
He said carol singing had been a part of the Christmas season in Satna "for the last 30 years".
Police in Satna told AFP they had detained the group for questioning after a resident complained about being "lured by a group of Christians to convert".
Eight other priests who went to the police station to look for the detained group were also taken into custody, investigating officer Mohini Sharma told AFP.
During their detention, a mob allegedly set fire to their car outside in an attack condemned by Mascarenhas as an assault by "terrorists who have taken on the garb of 'religious police'".
All 40 people have been released while no arrests have been made in the arson case, Sharma said.
Right-wing Hindu groups accuse churches and missionaries of targeting poor communities with financial incentives in a bid to convert them to Christianity, claims denied by the clergy.
Five Indian states, including Madhya Pradesh, have laws requiring individuals to get permission from government officials before they can convert to another faith.
Inducing an illegal conversion can mean a jail term of up to one year.
Around 80 percent of India's 1.2 billion population is Hindu, but it is also home to large numbers of Muslims, Christians and Buddhists.
