India's Hindu nationalists are petitioning courts to tear down mosques and replace them with temples

As day breaks on the Ganges, a dozen Hindu devotees slowly dip in the river's holy water and quietly chant. This is Varanasi, the ancient spiritual centre in India's northern Uttar Pradesh state, considered the holiest of cities.

It's also where a bitter legal dispute over a 17th-century mosque is increasing religious tensions between the city's Hindus and Muslims. 

"The friction has already been caused," said Varanasi resident Vijay Dutt Tiwari. "The fight will continue." 

Gyanvapi mosque, which has stood on the banks of the Ganges for more than 300 years, is the subject of around two dozen legal challenges that assert the structure was built on ruins of a temple devoted to the Hindu god Shiva. 

Many of the petitioners want the entire mosque, constructed by the Mughal emperor Aurangzeb, torn down and replaced with a temple. 

The mosque is heavily guarded by police and fenced off with concrete barriers and barbed wire. Muslims, who still pray at Gyanvapi five times a day, need to go through strict security before entering the compound. 

That security is even tighter in the midst of India's general election, where Prime Minister Narendra Modi is vying for a third straight term, and following a January court ruling that allowed Hindu worshippers access to the contested mosque's cellar to pray. 

The decision came after a court-ordered archeological survey concluded there was evidence of a "large Hindu temple prior to the construction of the existing structure." 

The legal battle is the latest religious flashpoint in an India increasingly divided along communal lines. But there are others brewing.  

Gyanvapi mosque may be the most high-profile case, but it's only one of hundreds of Muslim sites targeted by Hindu nationalist groups, who some historians accuse of aggressively attempting to rewrite India's history. 

Dozens of petitions have been filed, with varying arguments, against mosques and Muslim structures across the country. Judges have allowed the cases to be lodged despite the fact that India has a law that freezes places of worship as they were when India became independent in 1947, protecting them from any changes or disputes. 

Another mosque built by the Mughal emperor Aurangzeb, Shahi Eidgah in Mathura, Uttar Pradesh, is facing more than a dozen lawsuits. 

Even iconic monuments such as south Delhi's Qutub Minar, a heritage site with its imposing red sandstone brick minaret, and Agra's world-famous Taj Mahal have been mentioned in court. 

Those legal arguments are getting louder after Modi, who specifically chose the holy city of Varanasi as the constituency he wanted to represent when he first ran for office 10 years ago, inaugurated a new temple in the city of Ayodhya, devoted to the Hindu deity Lord Ram.