India's Internet users have topped 100 million, a study said Tuesday, and its online population could overtake the United States' within two years. India's Internet population stood at 112 million by September, making it the third-biggest globally after China and the United States, the Internet and Mobile Association of India said. It's good news that we've crossed the 100 million milestone, but it has taken us a long time to get here, association president Subho Ray told AFP. Internet use in India now is entering a critical growth phase, he added. India is adding 5 to 7 million Internet users every month, increasingly in small-town India and among the less wealthy. At the current pace, the country will overtake the United States in less than two years, the study projected. China's online population is the world's largest at 485 million while the United States has around 245 million users. The Indian government expects the number of Internet users in the country to total around 600 million in the next five years, Ray noted. The 600 million target is realistic if the government follows through with its ambitious plans to put in place the infrastructure for Internet usage, he said. Internet giant Google said last week it expects India's Internet growth to be driven by mobile phone users, predicting they will form the majority of new online users in the country as low-priced smartphones become available. As Internet usage has grown, online shopping has climbed sharply with retail chains and consumer goods companies jumping on the Web bandwagon to lure new e-customers. According to the Associated Chambers of Commerce and Industry of India, the online retail industry is expected to grow by 35 percent annually to touch 70 billion rupees ($1.4 billion) by 2015, up from 20 billion rupees now.