Children were among those injured when a group of about 50 men barged into the church in the central state of Chhattisgarh during Sunday mass.
"Nine people have been arrested so far," district police chief Badri Narayan Meena told AFP.
"The investigation is on and more arrests can't be ruled out."
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Three of the men were arrested shortly after the attack, which appears to have been triggered by rumours the church had been involved in converting local people to Christianity, and six more on Monday.
Witness Shiv Kumar described how the men stormed into the church with their faces covered, shouting slogans and terrifying worshippers.
The men smashed chairs and musical instruments, leading to scuffles with worshippers who tried to stop them.
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The latest incident comes a year after an elderly Christian nun was raped at a convent school in the eastern state of West Bengal, triggering protests across the country.
Last year saw a string of attacks on churches, heightening tensions over religious freedom in India.
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Around 80 per cent of India's 1.2 billion population is Hindu, but it is also home to large numbers of Muslims, Christians and Buddhists.
"No one will be spared and stern legal action will be taken against all those people who are involved in the incident," the state's Chief Minister Raman Singh said Monday.
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