SINGUR (AFP) - Thousands of people blocked traffic in eastern India on Saturday to protest at the scrapping of a Tata Motors factory to make the world's cheapest car, a move trade groups said could hurt investment. India's Tata Motors announced its plans to leave the Nano car plant site in Singur on the outskirts of the West Bengal state capital Kolkata on Friday after weeks of violent protests by farmers whose land was seized and political activists. Armed with iron bars and sticks, protestors shouted, "We want the Nano to roll out from Singur" and vowed to take on those opposed to the high-profile plant which supporters had said would transform the poverty-hit region. Police in riot gear patrolled the streets of Singur as protestors dug up roads to block traffic and thousands of trucks were stranded on the highway to Kolkata. "The project had triggered an economic boom. Our sales tripled," said Kamu Maji, who runs a tea shop near the Nano plant whose construction was nearly complete. The announcement by Tata Group chairman Ratan Tata of the plan to shift production came after building of the factory was halted in late August when protests made work impossible. Farmers and activists led by Mamata Banerjee, the fiery chief of the regional Trinamool Congress party, accused the state government of forcing farmers to give up their fertile land for a pittance to make way for the plant. "You cannot run a plant when bombs are being thrown, you cannot run a plant when workers are being intimidated," Ratan Tata told reporters in Kolkata on Friday. He said there was no possibility the company would change its mind. However, farmers in the area said they now faced the worst of both worlds. "We're frustrated and confused," said Laxman Das, 60, whose land was expropriated. "I don't think I will get back my land," he said, adding he still had not received any compensation for it. Trade groups said the problems that engulfed the Nano, slated to be sold for 100,000 rupees (2,150 dollars), were a blow to India's efforts to woo badly needed investment. "Given the global turmoil, foreign investors could decide to go to safer destinations and not come here," said Dilip Chenoy, director general of the Society of Indian Automobile Manufacturers. The decision by Tata Motors to withdraw from Singur was front-page news in Indian newspapers. "Tata drives Nano out of Bengal," said Business Standard in a front-page headline. The Calcutta Telegraph lamented the death of "Bengal's symbol of industrial resurgence." Industrialisation has been long championed by government officials as a way to pull tens of millions of Indians out of grinding poverty. But across India, land for factories has turned into a battleground and the Nano row was projected by some observers as a test case for industrialisation. The Tatas had said they hoped to roll out the car this month or by December at the latest. They did not say where they would build the new plant. Tata officials have said the first Nanos could be made at other Tata plants and the company has been flooded by invitations from other states to set up a full-scale Nano plant. Tata Motors poured 350 million dollars into the Singur plant. Its finances are already under pressure from digesting its 2.3-billion-dollar purchase of British motoring icons Jaguar and Land Rover, and from slowing domestic sales, analysts say.