Indian Muslim protesters clashed with police on Sunday with at least two people killed in riots sparked by a survey investigating if a 17th-century mosque was built on a Hindu temple.

“Two persons were confirmed dead,” Pawan Kumar, a police officer in Sambhal in the northern state of Uttar Pradesh, told AFP, adding that 16 police officers were “seriously injured” during the clashes.

The Press Trust of India news agency quoted officials saying three people had died.

Right-wing Hindu groups tend to lay claim to several mosques they allege were built over Hindu temples during the Muslim Mughal empire centuries ago.

Street battles broke out when a team of surveyors entered the Shahi Jama Masjid in Sambhal on orders from a local court, after a petition from a Hindu priest claiming it was built on the site of a Hindu temple.

Protesters on Sunday hurled rocks at police, who fired tear gas canisters to clear the crowd.

Hindu nationalist activists were emboldened earlier this year when Prime Minister Narendra Modi inaugurated a grand new Hindu temple in the northern city of Ayodhya, built on grounds once home to the centuries-old Babri mosque.

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That mosque was torn down in 1992 in a campaign spearheaded by members of Modi’s party, sparking sectarian riots that killed 2,000 people nationwide, most of them Muslims.

Some Hindu campaigners see an ideological patron in Modi.

Calls for India to enshrine Hindu supremacy have rapidly grown louder since Modi was swept to office in 2014, making the country’s roughly 210-million-strong Muslim minority increasingly anxious about their future.