Thousands of tourists fled the Indian hill resort of Darjeeling on Monday after local activists demanding the creation of a new Indian state warned that a general strike could degenerate into violence.

Riots and arson attacks in Darjeeling last week left 12 people injured and the Gorkha Janmukti Morcha (GJM) group warned at the weekend that "untoward" events could happen when the general strike started Monday.

The hills are famous for the Darjeeling tea whose production is jealously guarded. It is also famed for its "toy train" -- a 78-kilometer uphill ride from New Jalpaiguri.

Pradip Lama, secretary of the Darjeeling Tourist Association of Travel Agents, told AFP that worried visitors -- most of them from other parts of India -- are leaving and nearly 70 percent of bookings have been cancelled.

"Till Sunday, 7,000 tourists left Darjeeling," Lama said.

The GJM wants a new state named Gorkhaland in the hill region, which is now part of West Bengal.

Tensions have also risen over a government decision to introduce the Bengali language in schools. Indigenous Gorkhas, who mainly speak Nepali, are furious.

"We had heard about the trouble and still reached the hill resort on Friday, hoping that the situation would be normal," Priya Roy, a visitor from the southern city of Bangalore, told AFP.

"We have decided to leave Darjeeling after GJM's warning to tourists."

Another tourist said their group's vehicle was mobbed by slogan-shouting protesters who demanded to know their identities.

"I clutched at my mother's arm even as she begged with folded hands, pleading with them to let us go," Kamalika Chatterjee told AFP.

Bimal Gurung, head of the GJM, told AFP his warning to the tourists was "for their own safety" as the events could worsen anytime if his group launches a full-scale campaign for a separate state.

Darjeeling district magistrate Joyoshi Dasgupta said at least a dozen GJM activists had been detained for allegedly instigating the violence.

"A group of suspected GJM activists tried to set fire to government offices... on Monday. Security was stepped up in front of all government offices in the hills of Darjeeling as a precautionary measure," Dasgupta said.

The GJM denied its members were involved in violence.

The Gorkhas have been campaigning for decades for the new state. They say Bengali-speaking outsiders have exploited their resources and imposed their culture and language.

A similar agitation in 2007 led to the granting of some administrative powers to local people.

Many groups in India have waged similar campaigns to break away from larger states, mostly on linguistic and ethnic grounds or in hopes of economic benefits.

The last successful agitation led to the formation of Telangana state in 2014.

India is made up of 29 states and seven federally administered territories, which include the capital region New Delhi.