India's tourism industry has been hit by a wave of violent anti-government protests against a new citizenship law that have rocked several cities this month, with at least seven countries issuing travel warnings.

At least 25 people have been killed in clashes between police and protesters, and demonstrations against the law continue.

Officials estimate about 200,000 domestic and international tourists cancelled or postponed their trip to the Taj Mahal in the past two weeks, one of the world's most popular tourist attractions.

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“There has been a 60 per cent decline in visitor footfalls in December this year,” said Dinesh Kumar, a police inspector overseeing a special tourist police station near the Taj Mahal who has access to visitor data. He said the decline was compared to December last year.

“Indian and foreign tourists have been calling our control rooms to check security. We assure them of protection, but many still decide to stay away,” said Kumar.

The 17th century marble monument is in Uttar Pradesh, the northern state that has witnessed the highest number of deaths and intense bursts of violence in two weeks of unrest.

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A group of European tourists travelling in a group across India said they now planned to cut short their 20 day trip.

“We are all retired folks, for us travel has to be slow and relaxing. The newspaper headlines have led to a sense of concern and we will leave sooner than we had planned,” said Dave Millikin, a retired banker living on the outskirts of London, who spoke to Reuters from the capital New Delhi.

The Taj Mahal, situated in the town of Agra, attracts over 6.5 million tourists every year, generating nearly $14 million annually from entrance fees. A foreign tourist pays about $15 to enter the grounds, although nationals from neighbouring countries get a discount.

Managers in luxury hotels and guest houses around the Taj Mahal said last minute cancellations during the festive season have further dampened business sentiment at a time when the country's economic growth has slowed to 4.5pc, its slowest pace in more than six years.

In a bid to clamp down on violence and unrest, authorities have suspended mobile internet services in Agra.

“Blocking the internet has affected travel and tourism in Agra by about 50-60pc,” said Sandeep Arora, president of the Agra Tourism Development Foundation that groups over 250 tour operators, hotels and guides.

The United States, Britain, Russia, Israel, Singapore, Canada and Taiwan have issued travel advisories asking their citizens to either refrain from visiting or to exercise caution when visiting regions embroiled in India's protests.

Jayanta Malla Baruah, the head of the Assam Tourism Development Corporation, said the state, home to the world's largest concentration of one-horned rhinoceroses, is visited on average by 500,000 tourists during December.

“But this time, due to the ongoing protests and travel advisories by various countries, the number is down by 90pc if not more.”