Cow dung cakes have been used for centuries to fuel fires for cooking and are specially laid out on the festival of colours, Holi. (AP Photo)

Online vendors like Amazon, ShopClues and eBay are selling cow dung patties to India's ever-increasing urban population. (AP Photo)

There's one unusual item flying off the virtual shelves: Online retailers say cow dung patties are selling like hot cakes.The patties - cow poop mixed with hay and dried in the sun, made mainly by women in rural areas and used to fuel fires - have long been available in villages. But online retailers including Amazon and eBay are now reaching out to the country's ever-increasing urban population, feeding into the desire of older city folks to harken back to their childhood in the village.Some retailers say they're offering discounts for large orders. Some customers are asking for gift wrapping."Cow dung cakes have been listed by multiple sellers on our platform since October and we have received several customer orders" since then, said Madhavi Kochar, an Amazon India spokeswoman.The orders come mostly from cities where it would be difficult to buy dung cakes, she said.Cow dung cakes have been used for centuries for fires, whether for heating, cooking or for rituals. Across rural landscape, piles of drying cow dung are ubiquitous.Radhika Agarwal of ShopClues, a major online retailer in the country, said demand for the cow dung cakes spiked during the recent Diwali festival season, a time when many people conduct prayer ceremonies at their homes, factories and offices. On a recent day, ShopClues' website showed that the patties had sold out."Around Diwali, when people do a lot of pujas in their homes and workplaces, there is a lot of demand for cow dung cakes," said Ms Agarwal, referring to rituals performed during the popular festival."Increasingly, in the cold weather, people are keeping themselves warm by lighting fires" at outdoor events, she said, adding that people who grew up in rural areas find the peaty smell of dung fires pleasant."It reminds them of the old days," she said.Online retailers said people were also buying the dung cakes to light fires for ritual ceremonies to mark the beginning of a new year and for the winter festival Lohri, celebrated in northern India.The cakes are sold in packages that contain two to eight pieces weighing 200 grams (7 ounces) each. Prices range from Rs 100 to Rs 400 per package.Dung cakes are also used as organic manure, and some sellers are marketing them for use in kitchen gardens.